diff --git a/app/src/app/[locale]/importer/[id]/closed/page.tsx b/app/src/app/[locale]/importer/[id]/closed/page.tsx
index b1ebfc0..bd7f444 100644
--- a/app/src/app/[locale]/importer/[id]/closed/page.tsx
+++ b/app/src/app/[locale]/importer/[id]/closed/page.tsx
@@ -1,7 +1,5 @@
-import { ImporterDto } from "@/app/api/importer/[slug]/ImporterDto";
 import initTranslations from "@/i18n/initi18n";
-import { fetchWithAuth } from "@/lib/frontendFetch";
-import { getHost } from "@/lib/utils";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { CheckCircleIcon } from "lucide-react";
 import { redirect } from "next/navigation";
 import { getPageForState } from "../redirectUtil";
@@ -16,13 +14,9 @@ type Props = {
 const ImporterClosedPage = async (props: Props) => {
   const { t } = await initTranslations(props.params.locale);
   const importerId = props.params.id;
-  const initialImporterDto = (await fetchWithAuth(
-    `${getHost()}/api/importer/${importerId}`,
-    {
-      cache: "no-cache",
-    }
-  ).then((res) => res.json())) as ImporterDto;
-  const pageForState = getPageForState(initialImporterDto);
+  const importerManager = await getImporterManager();
+  const importerDto = await importerManager.getImporterDto(importerId);
+  const pageForState = getPageForState(importerDto);
   if (pageForState !== "closed") {
     return redirect(pageForState);
   }
diff --git a/app/src/app/[locale]/importer/[id]/importing/page.tsx b/app/src/app/[locale]/importer/[id]/importing/page.tsx
index 16c587c..2b64ae3 100644
--- a/app/src/app/[locale]/importer/[id]/importing/page.tsx
+++ b/app/src/app/[locale]/importer/[id]/importing/page.tsx
@@ -1,8 +1,6 @@
-import { ImporterDto } from "@/app/api/importer/[slug]/ImporterDto";
 import { Button } from "@/components/ui/button";
 import initTranslations from "@/i18n/initi18n";
-import { fetchWithAuth } from "@/lib/frontendFetch";
-import { getHost } from "@/lib/utils";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { ZapIcon } from "lucide-react";
 import { redirect } from "next/navigation";
 import { getPageForState } from "../redirectUtil";
@@ -17,20 +15,14 @@ type Props = {
 const ImportingPage = async (props: Props) => {
   const { t } = await initTranslations(props.params.locale);
   const importerId = props.params.id;
-  const initialImporterDtoPromise = fetchWithAuth(
-    `${getHost()}/api/importer/${importerId}`,
-    {
-      cache: "no-cache",
-    }
-  ).then(async (res) => (await res.json()) as ImporterDto);
-
-  const initialImporterDto = await initialImporterDtoPromise;
-  const page = getPageForState(initialImporterDto);
+  const importerManager = await getImporterManager();
+  const importerDto = await importerManager.getImporterDto(importerId);
+  const page = getPageForState(importerDto);
   if (page !== "importing") {
     return redirect(page);
   }
 
-  const redirectUrl = initialImporterDto.config.redirectUrl;
+  const redirectUrl = importerDto.config.redirectUrl;
   return (
     <div className="w-full h-full flex items-center justify-center">
       <div className="flex flex-col items-center">
diff --git a/app/src/app/[locale]/importer/[id]/layout.tsx b/app/src/app/[locale]/importer/[id]/layout.tsx
index 960802f..8339b27 100644
--- a/app/src/app/[locale]/importer/[id]/layout.tsx
+++ b/app/src/app/[locale]/importer/[id]/layout.tsx
@@ -1,8 +1,7 @@
-import { ImporterDto } from "@/app/api/importer/[slug]/ImporterDto";
 import TranslationsProvider from "@/components/TranslationsProvider";
 import { Toaster } from "@/components/ui/toaster";
-import { fetchWithAuth } from "@/lib/frontendFetch";
-import { getHost, hexToCssHsl } from "@/lib/utils";
+import { getImporterManager } from "@/lib/ImporterManager";
+import { hexToCssHsl } from "@/lib/utils";
 import SidebarMenu from "./SidebarMenu";
 
 type PageProps = {
@@ -14,12 +13,8 @@ type PageProps = {
 };
 
 export default async function ImporterPage({ params, children }: PageProps) {
-  const importerDto = (await fetchWithAuth(
-    `${getHost()}/api/importer/${params.id}`,
-    {
-      cache: "no-cache",
-    }
-  ).then((res) => res.json())) as ImporterDto;
+  const importerManager = await getImporterManager();
+  const importerDto = await importerManager.getImporterDto(params.id);
   const { primaryColor, primaryForegroundColor } =
     importerDto.config.design ?? {};
   return (
diff --git a/app/src/app/[locale]/importer/[id]/mapping/SelectMappings.tsx b/app/src/app/[locale]/importer/[id]/mapping/SelectMappings.tsx
index a5baed5..de374d5 100644
--- a/app/src/app/[locale]/importer/[id]/mapping/SelectMappings.tsx
+++ b/app/src/app/[locale]/importer/[id]/mapping/SelectMappings.tsx
@@ -26,7 +26,7 @@ import { produce } from "immer";
 import { ChevronRightCircleIcon } from "lucide-react";
 import { useRouter } from "next/navigation";
 
-import { fetchWithAuth } from "@/lib/frontendFetch";
+import { useFrontendFetchWithAuth } from "@/lib/frontendFetch";
 import { getHost } from "@/lib/utils";
 import React from "react";
 import { useTranslation } from "react-i18next";
@@ -48,6 +48,7 @@ const SelectMappings = ({
 }: Props) => {
   const { push } = useRouter();
   const { t } = useTranslation();
+  const frontendFetch = useFrontendFetchWithAuth();
   const [enablePolling, setEnablePolling] = React.useState(false);
   const { importer } = useGetImporter(
     initialImporterDto.importerId,
@@ -103,7 +104,7 @@ const SelectMappings = ({
     }
     setIsSavingMapping(true);
     try {
-      await fetchWithAuth(
+      await frontendFetch(
         `${getHost()}/api/importer/${importer.importerId}/mappings`,
         {
           method: "PUT",
diff --git a/app/src/app/[locale]/importer/[id]/mapping/page.tsx b/app/src/app/[locale]/importer/[id]/mapping/page.tsx
index 20404b9..8525365 100644
--- a/app/src/app/[locale]/importer/[id]/mapping/page.tsx
+++ b/app/src/app/[locale]/importer/[id]/mapping/page.tsx
@@ -1,9 +1,4 @@
-import {
-  DataMappingRecommendation,
-  ImporterDto,
-} from "@/app/api/importer/[slug]/ImporterDto";
-import { fetchWithAuth } from "@/lib/frontendFetch";
-import { getHost } from "@/lib/utils";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { redirect } from "next/navigation";
 import { getPageForState } from "../redirectUtil";
 import SelectMappings from "./SelectMappings";
@@ -16,21 +11,10 @@ type Props = {
 
 const MappingPage = async (props: Props) => {
   const importerId = props.params.id;
-  const initialImporterDtoPromise = fetchWithAuth(
-    `${getHost()}/api/importer/${importerId}`,
-    {
-      cache: "no-cache",
-    }
-  ).then(async (res) => (await res.json()) as ImporterDto);
-  const initialDataMappingsPromise = fetchWithAuth(
-    `${getHost()}/api/importer/${importerId}/mappings/recommendations`,
-    {
-      cache: "no-cache",
-    }
-  ).then(
-    async (res) =>
-      (await res.json()).recommendations as DataMappingRecommendation[] | null
-  );
+  const importerManager = await getImporterManager();
+  const initialImporterDtoPromise = importerManager.getImporterDto(importerId);
+  const initialDataMappingsPromise =
+    importerManager.getMappingRecommendations(importerId);
   const [initialImporterDto, initialDataMappings] = await Promise.all([
     initialImporterDtoPromise,
     initialDataMappingsPromise,
diff --git a/app/src/app/[locale]/importer/[id]/select-file/SelectFileUploader.tsx b/app/src/app/[locale]/importer/[id]/select-file/SelectFileUploader.tsx
index 6e7658c..e03953f 100644
--- a/app/src/app/[locale]/importer/[id]/select-file/SelectFileUploader.tsx
+++ b/app/src/app/[locale]/importer/[id]/select-file/SelectFileUploader.tsx
@@ -3,7 +3,7 @@ import { ImporterDto } from "@/app/api/importer/[slug]/ImporterDto";
 import { useGetImporter } from "@/components/hooks/useGetImporter";
 import { LoadingSpinner } from "@/components/ui/loadingSpinner";
 import { useToast } from "@/components/ui/use-toast";
-import { fetchWithAuth } from "@/lib/frontendFetch";
+import { useFrontendFetchWithAuth } from "@/lib/frontendFetch";
 import { getHost } from "@/lib/utils";
 import { useRouter } from "next/navigation";
 import React from "react";
@@ -23,7 +23,8 @@ const allowedMimeTypes = [
 
 const SelectFileUploader = ({ importerDto: initialImporterDto }: Props) => {
   const { t } = useTranslation();
-  const { push, replace } = useRouter();
+  const { push } = useRouter();
+  const frontendFetch = useFrontendFetchWithAuth();
   const { toast } = useToast();
   const [isUploading, setIsUploading] = React.useState(false);
   const [hasUploaded, setHasUploaded] = React.useState(false);
@@ -40,7 +41,7 @@ const SelectFileUploader = ({ importerDto: initialImporterDto }: Props) => {
         const formData = new FormData();
         formData.append("file", file);
         formData.append("importerId", importer.importerId);
-        await fetchWithAuth(`${getHost()}/api/upload`, {
+        await frontendFetch(`${getHost()}/api/upload`, {
           method: "POST",
           body: formData,
         });
diff --git a/app/src/app/[locale]/importer/[id]/select-file/page.tsx b/app/src/app/[locale]/importer/[id]/select-file/page.tsx
index 5f095be..d9ce745 100644
--- a/app/src/app/[locale]/importer/[id]/select-file/page.tsx
+++ b/app/src/app/[locale]/importer/[id]/select-file/page.tsx
@@ -1,6 +1,4 @@
-import { ImporterDto } from "@/app/api/importer/[slug]/ImporterDto";
-import { fetchWithAuth } from "@/lib/frontendFetch";
-import { getHost } from "@/lib/utils";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { redirect } from "next/navigation";
 import { getPageForState } from "../redirectUtil";
 import SelectFileUploader from "./SelectFileUploader";
@@ -13,19 +11,15 @@ type Props = {
 
 const SelectFilePage = async (props: Props) => {
   const importerId = props.params.id;
-  const initialImporterDto = (await fetchWithAuth(
-    `${getHost()}/api/importer/${importerId}`,
-    {
-      cache: "no-cache",
-    }
-  ).then((res) => res.json())) as ImporterDto;
-  const pageForState = getPageForState(initialImporterDto);
+  const importerManager = await getImporterManager();
+  const importerDto = await importerManager.getImporterDto(importerId);
+  const pageForState = getPageForState(importerDto);
   if (pageForState !== "select-file") {
     return redirect(pageForState);
   }
   return (
     <div className="flex h-full items-center justify-center">
-      <SelectFileUploader importerDto={initialImporterDto} />
+      <SelectFileUploader importerDto={importerDto} />
     </div>
   );
 };
diff --git a/app/src/app/[locale]/importer/[id]/validate/Validation.tsx b/app/src/app/[locale]/importer/[id]/validate/Validation.tsx
index 08c7e6f..0b3fdc4 100644
--- a/app/src/app/[locale]/importer/[id]/validate/Validation.tsx
+++ b/app/src/app/[locale]/importer/[id]/validate/Validation.tsx
@@ -7,7 +7,7 @@ import { useGetImporter } from "@/components/hooks/useGetImporter";
 import { Button } from "@/components/ui/button";
 import { LoadingSpinner } from "@/components/ui/loadingSpinner";
 import { useToast } from "@/components/ui/use-toast";
-import { fetchWithAuth } from "@/lib/frontendFetch";
+import { useFrontendFetchWithAuth } from "@/lib/frontendFetch";
 import { getHost } from "@/lib/utils";
 import { enableMapSet, produce } from "immer";
 import { sum } from "lodash";
@@ -30,6 +30,7 @@ const Validation = ({
   const { t } = useTranslation();
   const { push } = useRouter();
   const { toast } = useToast();
+  const frontendFetch = useFrontendFetchWithAuth();
   const [enablePolling, setEnablePolling] = React.useState(false);
   const [isStartingImport, setIsStartingImport] = React.useState(false);
   const [currentValidations, setCurrentValidations] = React.useState<
@@ -154,7 +155,7 @@ const Validation = ({
         })
       );
       try {
-        const res = await fetchWithAuth(
+        const res = await frontendFetch(
           `${getHost()}/api/importer/${initialImporterDto.importerId}/records`,
           {
             method: "PATCH",
@@ -182,7 +183,12 @@ const Validation = ({
         }
       }
     },
-    [handleRecordUpdate, initialImporterDto.importerId, isMounted]
+    [
+      frontendFetch,
+      handleRecordUpdate,
+      initialImporterDto.importerId,
+      isMounted,
+    ]
   );
 
   const handleStartImport = React.useCallback(async () => {
@@ -191,7 +197,7 @@ const Validation = ({
     }
     setIsStartingImport(true);
     try {
-      await fetchWithAuth(
+      await frontendFetch(
         `${getHost()}/api/importer/${
           initialImporterDto.importerId
         }/start-import`,
@@ -211,7 +217,15 @@ const Validation = ({
         setIsStartingImport(false);
       }
     }
-  }, [initialImporterDto.importerId, isMounted, push, t, toast, totalErrors]);
+  }, [
+    frontendFetch,
+    initialImporterDto.importerId,
+    isMounted,
+    push,
+    t,
+    toast,
+    totalErrors,
+  ]);
 
   const hasErrors = dataStats.totalErrors > 0;
 
diff --git a/app/src/app/[locale]/importer/[id]/validate/page.tsx b/app/src/app/[locale]/importer/[id]/validate/page.tsx
index f4357ea..cecfc7e 100644
--- a/app/src/app/[locale]/importer/[id]/validate/page.tsx
+++ b/app/src/app/[locale]/importer/[id]/validate/page.tsx
@@ -1,20 +1,13 @@
-import { ImporterDto } from "@/app/api/importer/[slug]/ImporterDto";
-import { fetchRecords } from "@/components/hooks/useFetchRecords";
-import { fetchWithAuth } from "@/lib/frontendFetch";
-import { getHost } from "@/lib/utils";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { redirect } from "next/navigation";
 import { getPageForState } from "../redirectUtil";
 import Validation from "./Validation";
 
 export default async function page(props: { params: { id: string } }) {
   const importerId = props.params.id;
-  const initialImporterDtoPromise = fetchWithAuth(
-    `${getHost()}/api/importer/${importerId}`,
-    {
-      cache: "no-cache",
-    }
-  ).then((res) => res.json() as Promise<ImporterDto>);
-  const initialRecordsPromise = fetchRecords(importerId, 0, 100);
+  const importerManager = await getImporterManager();
+  const initialImporterDtoPromise = importerManager.getImporterDto(importerId);
+  const initialRecordsPromise = importerManager.getRecords(importerId, 0, 100);
   const [initialImporterDto, initialRecords] = await Promise.all([
     initialImporterDtoPromise,
     initialRecordsPromise,
diff --git a/app/src/app/api/importer/[slug]/close/route.ts b/app/src/app/api/importer/[slug]/close/route.ts
index e90bb65..6752225 100644
--- a/app/src/app/api/importer/[slug]/close/route.ts
+++ b/app/src/app/api/importer/[slug]/close/route.ts
@@ -1,4 +1,4 @@
-import { getTemporalWorkflowClient } from "@/lib/temporalClient";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { validateServerAuth } from "@/lib/validateAuth";
 import { NextRequest, NextResponse } from "next/server";
 
@@ -10,8 +10,7 @@ export async function POST(
     return NextResponse.json("Unauthorized", { status: 401 });
   }
   const { slug: importerId } = params;
-  const client = await getTemporalWorkflowClient();
-  const handle = client.getHandle(importerId);
-  await handle.signal("importer:close");
+  const importerManager = await getImporterManager();
+  await importerManager.closeImporter(importerId);
   return NextResponse.json({});
 }
diff --git a/app/src/app/api/importer/[slug]/mappings/recommendations/route.ts b/app/src/app/api/importer/[slug]/mappings/recommendations/route.ts
index ae37ce0..72781ab 100644
--- a/app/src/app/api/importer/[slug]/mappings/recommendations/route.ts
+++ b/app/src/app/api/importer/[slug]/mappings/recommendations/route.ts
@@ -1,7 +1,6 @@
-import { getTemporalWorkflowClient } from "@/lib/temporalClient";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { validateAuth } from "@/lib/validateAuth";
 import { NextRequest, NextResponse } from "next/server";
-import { ImporterStatus } from "../../ImporterDto";
 
 export async function GET(
   req: NextRequest,
@@ -11,14 +10,17 @@ export async function GET(
     return NextResponse.json("Unauthorized", { status: 401 });
   }
   const { slug: importerId } = params;
-  const client = await getTemporalWorkflowClient();
-  const handle = client.getHandle(importerId);
-  const workflowState = await handle.query<ImporterStatus>("importer:status");
-  if (workflowState.state === "closed") {
-    return NextResponse.json({ error: "Importer is closed" }, { status: 410 });
+  const importerManager = await getImporterManager();
+  try {
+    const recommendations = await importerManager.getMappingRecommendations(
+      importerId
+    );
+    return NextResponse.json({ recommendations });
+  } catch (err) {
+    if ((err as Error).message === "Importer is closed") {
+      return NextResponse.json("Importer is closed", { status: 400 });
+    } else {
+      throw err;
+    }
   }
-  const recommendations = await handle.query(
-    "importer:data-mapping-recommendations"
-  );
-  return NextResponse.json({ recommendations });
 }
diff --git a/app/src/app/api/importer/[slug]/mappings/route.ts b/app/src/app/api/importer/[slug]/mappings/route.ts
index 245125f..47aa70f 100644
--- a/app/src/app/api/importer/[slug]/mappings/route.ts
+++ b/app/src/app/api/importer/[slug]/mappings/route.ts
@@ -1,7 +1,6 @@
-import { getTemporalWorkflowClient } from "@/lib/temporalClient";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { validateAuth } from "@/lib/validateAuth";
 import { NextRequest, NextResponse } from "next/server";
-import { ImporterStatus } from "../ImporterDto";
 
 export async function PUT(
   req: NextRequest,
@@ -11,16 +10,9 @@ export async function PUT(
     return NextResponse.json("Unauthorized", { status: 401 });
   }
   const { slug: importerId } = params;
-  const client = await getTemporalWorkflowClient();
-  const handle = client.getHandle(importerId);
+  const importerManager = await getImporterManager();
   const mappings = await req.json();
-  const workflowState = await handle.query<ImporterStatus>("importer:status");
-  if (workflowState.state === "closed") {
-    return NextResponse.json({ error: "Importer is closed" }, { status: 410 });
-  }
-  await handle.executeUpdate("importer:update-mapping", {
-    args: [{ mappings }],
-  });
+  await importerManager.updateMappings(importerId, mappings);
   return new NextResponse(undefined, {
     status: 201,
   });
diff --git a/app/src/app/api/importer/[slug]/records/route.ts b/app/src/app/api/importer/[slug]/records/route.ts
index 627a063..3d84c51 100644
--- a/app/src/app/api/importer/[slug]/records/route.ts
+++ b/app/src/app/api/importer/[slug]/records/route.ts
@@ -1,8 +1,6 @@
-import { getTemporalWorkflowClient } from "@/lib/temporalClient";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { validateAuth } from "@/lib/validateAuth";
 import { NextRequest, NextResponse } from "next/server";
-import { getDb } from "../../../../../lib/mongoClient";
-import { DataSetPatch, ImporterStatus } from "../ImporterDto";
 
 export async function GET(
   req: NextRequest,
@@ -12,23 +10,10 @@ export async function GET(
     return NextResponse.json("Unauthorized", { status: 401 });
   }
   const { slug: importerId } = params;
-  const client = await getTemporalWorkflowClient();
-  const handle = client.getHandle(importerId);
-  const workflowState = await handle.query<ImporterStatus>("importer:status");
-  if (workflowState.state === "closed") {
-    return NextResponse.json({ error: "Importer is closed" }, { status: 410 });
-  }
-  const db = await getDb(importerId);
+  const importerManager = await getImporterManager();
   const page = parseInt(req.nextUrl.searchParams.get("page") ?? "0");
   const size = parseInt(req.nextUrl.searchParams.get("size") ?? "100");
-  // TODO validate access or so :)
-  const records = await db
-    .collection("data")
-    .find()
-    .sort({ __sourceRowId: 1 })
-    .skip(page * size)
-    .limit(size)
-    .toArray();
+  const records = await importerManager.getRecords(importerId, page, size);
   return NextResponse.json({ records });
 }
 
@@ -40,29 +25,15 @@ export async function PATCH(
     return NextResponse.json("Unauthorized", { status: 401 });
   }
   const { slug: importerId } = params;
-  const client = await getTemporalWorkflowClient();
-  const handle = client.getHandle(importerId);
+  const importerManager = await getImporterManager();
   const updateData = await req.json();
-  const updateResult = await handle.executeUpdate<
+  const patches = [
     {
-      changedColumns: string[];
-      newMessages: Record<string, any[]>;
+      column: updateData.columnId,
+      rowId: updateData._id,
+      newValue: updateData.value,
     },
-    [{ patches: DataSetPatch[] }]
-  >("importer:update-record", {
-    args: [
-      {
-        patches: [
-          {
-            column: updateData.columnId,
-            rowId: updateData._id,
-            newValue: updateData.value,
-          },
-        ],
-      },
-    ],
-  });
-  // CALL update for patches
-  // TODO return new messages for cell and return if it whole column changed (client can reload pages and stats)
+  ];
+  const updateResult = await importerManager.patchRecords(importerId, patches);
   return NextResponse.json(updateResult);
 }
diff --git a/app/src/app/api/importer/[slug]/route.ts b/app/src/app/api/importer/[slug]/route.ts
index e2f8f00..d71baa5 100644
--- a/app/src/app/api/importer/[slug]/route.ts
+++ b/app/src/app/api/importer/[slug]/route.ts
@@ -1,7 +1,6 @@
-import { getTemporalWorkflowClient } from "@/lib/temporalClient";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { validateAuth } from "@/lib/validateAuth";
 import { NextRequest, NextResponse } from "next/server";
-import { ImporterConfig, ImporterDto, ImporterStatus } from "./ImporterDto";
 
 export async function GET(
   req: NextRequest,
@@ -11,16 +10,7 @@ export async function GET(
     return NextResponse.json("Unauthorized", { status: 401 });
   }
   const { slug: importerId } = params;
-  const client = await getTemporalWorkflowClient();
-  const handle = client.getHandle(importerId);
-  const [status, config] = await Promise.all([
-    (await handle.query("importer:status")) as ImporterStatus,
-    (await handle.query("importer:config")) as ImporterConfig,
-  ]);
-  const importerDto: ImporterDto = {
-    importerId,
-    config,
-    status,
-  };
+  const importerManager = await getImporterManager();
+  const importerDto = await importerManager.getImporterDto(importerId);
   return NextResponse.json(importerDto);
 }
diff --git a/app/src/app/api/importer/[slug]/start-import/route.ts b/app/src/app/api/importer/[slug]/start-import/route.ts
index 32b4c1b..c5093d9 100644
--- a/app/src/app/api/importer/[slug]/start-import/route.ts
+++ b/app/src/app/api/importer/[slug]/start-import/route.ts
@@ -1,7 +1,6 @@
-import { getTemporalWorkflowClient } from "@/lib/temporalClient";
+import { getImporterManager } from "@/lib/ImporterManager";
 import { validateAuth } from "@/lib/validateAuth";
 import { NextRequest, NextResponse } from "next/server";
-import { ImporterStatus } from "../ImporterDto";
 
 export async function POST(
   req: NextRequest,
@@ -11,12 +10,7 @@ export async function POST(
     return NextResponse.json("Unauthorized", { status: 401 });
   }
   const { slug: importerId } = params;
-  const client = await getTemporalWorkflowClient();
-  const handle = client.getHandle(importerId);
-  const workflowState = await handle.query<ImporterStatus>("importer:status");
-  if (workflowState.state === "closed") {
-    return NextResponse.json({ error: "Importer is closed" }, { status: 410 });
-  }
-  await handle.executeUpdate("importer:start-import");
+  const importerManager = await getImporterManager();
+  await importerManager.startImport(importerId);
   return NextResponse.json({ importerId });
 }
diff --git a/app/src/app/api/upload/route.ts b/app/src/app/api/upload/route.ts
index b432159..944b809 100644
--- a/app/src/app/api/upload/route.ts
+++ b/app/src/app/api/upload/route.ts
@@ -1,8 +1,8 @@
-import { getTemporalWorkflowClient } from "@/lib/temporalClient";
 import { randomUUID } from "crypto";
 import { NextRequest, NextResponse } from "next/server";
 import { extname } from "path";
 
+import { getImporterManager } from "@/lib/ImporterManager";
 import { validateAuth } from "@/lib/validateAuth";
 import { getMinioClient } from "../../../lib/minioClient";
 
@@ -10,16 +10,24 @@ export async function POST(req: NextRequest) {
   if (validateAuth(req) === false) {
     return NextResponse.json("Unauthorized", { status: 401 });
   }
+  const { importerId, bucket, destFileName, fileFormat } =
+    await handleFileUpload(req);
+  const importerManager = await getImporterManager();
+  await importerManager.addFile(importerId, destFileName, fileFormat, bucket);
+  return new Response(undefined, { status: 201 });
+}
+
+async function handleFileUpload(req: NextRequest) {
   const formData = await req.formData();
   const file: File | null = formData.get("file") as unknown as File;
   const importerId = formData.get("importerId") as unknown as string;
   const fileBuffer = Buffer.from(await file.arrayBuffer());
 
   if (!importerId) {
-    return new Response("importerId missing", { status: 500 });
+    throw new Error("importerId missing");
   }
   if (!fileBuffer) {
-    return new Response("file missing", { status: 500 });
+    throw new Error("file missing");
   }
 
   const bucket = importerId;
@@ -45,18 +53,14 @@ export async function POST(req: NextRequest) {
     );
   } catch (error) {
     console.error(error);
-    return new Response("Failed to upload file", { status: 500 });
+    throw new Error("Error uploading file");
   }
-  const client = await getTemporalWorkflowClient();
-  const handle = client.getHandle(importerId);
-  await handle.executeUpdate("importer:add-file", {
-    args: [
-      {
-        fileReference: destFileName,
-        fileFormat: extname(file.name) === ".csv" ? "csv" : "xlsx",
-        bucket,
-      },
-    ],
-  });
-  return new Response("", { status: 201 });
+  const fileFormat = extname(file.name) === ".csv" ? "csv" : "xlsx";
+
+  return {
+    importerId,
+    bucket,
+    destFileName,
+    fileFormat,
+  };
 }
diff --git a/app/src/components/hooks/useFetchRecords.tsx b/app/src/components/hooks/useFetchRecords.tsx
index bab1c3f..c59c07e 100644
--- a/app/src/components/hooks/useFetchRecords.tsx
+++ b/app/src/components/hooks/useFetchRecords.tsx
@@ -1,17 +1,19 @@
 import { SourceData } from "@/app/api/importer/[slug]/ImporterDto";
-import { fetchWithAuth } from "@/lib/frontendFetch";
+import { useFrontendFetchWithAuth } from "@/lib/frontendFetch";
 import { getHost } from "@/lib/utils";
 
 export function useFetchRecords(importerId: string | null) {
+  const frontendFetch = useFrontendFetchWithAuth();
   if (!importerId) {
     return () => [];
   }
   return async (page: number, pageSize: number) => {
-    return fetchRecords(importerId, page, pageSize);
+    return fetchRecords(frontendFetch, importerId, page, pageSize);
   };
 }
 
 export async function fetchRecords(
+  frontendFetch: ReturnType<typeof useFrontendFetchWithAuth>,
   importerId: string,
   page: number,
   pageSize: number
@@ -19,7 +21,7 @@ export async function fetchRecords(
   const getUrl = new URL(`/api/importer/${importerId}/records`, getHost());
   getUrl.searchParams.append("page", page.toFixed());
   getUrl.searchParams.append("pageSize", pageSize.toFixed());
-  const result = fetchWithAuth(getUrl, {
+  const result = frontendFetch(getUrl, {
     method: "GET",
     cache: "no-cache",
   }).then((res) => res.json() as Promise<{ records: SourceData[] }>);
diff --git a/app/src/components/hooks/useGetImporter.tsx b/app/src/components/hooks/useGetImporter.tsx
index c4f846c..2c5ce62 100644
--- a/app/src/components/hooks/useGetImporter.tsx
+++ b/app/src/components/hooks/useGetImporter.tsx
@@ -1,5 +1,5 @@
 import { ImporterDto } from "@/app/api/importer/[slug]/ImporterDto";
-import { fetchWithAuth } from "@/lib/frontendFetch";
+import { useFrontendFetchWithAuth } from "@/lib/frontendFetch";
 import { getHost } from "@/lib/utils";
 import useSWR from "swr";
 
@@ -8,9 +8,10 @@ export function useGetImporter(
   pollInterval?: number,
   fallbackData?: ImporterDto
 ) {
+  const frontendFetch = useFrontendFetchWithAuth();
   const { data, error, isLoading, mutate } = useSWR(
     importerId ? [`${getHost()}/api/importer/${importerId}`] : null,
-    ([url]) => fetchWithAuth(url).then((res) => res.json()),
+    ([url]) => frontendFetch(url).then((res) => res.json()),
     {
       refreshInterval: pollInterval,
       fallbackData,
diff --git a/app/src/components/hooks/useGetMappingRecommendations.tsx b/app/src/components/hooks/useGetMappingRecommendations.tsx
index 1f8d799..c72b579 100644
--- a/app/src/components/hooks/useGetMappingRecommendations.tsx
+++ b/app/src/components/hooks/useGetMappingRecommendations.tsx
@@ -1,5 +1,5 @@
 import { DataMappingRecommendation } from "@/app/api/importer/[slug]/ImporterDto";
-import { fetchWithAuth } from "@/lib/frontendFetch";
+import { useFrontendFetchWithAuth } from "@/lib/frontendFetch";
 import { getHost } from "@/lib/utils";
 import useSWR from "swr";
 
@@ -8,11 +8,12 @@ export function useGetMappingRecommendations(
   pollInterval?: number,
   fallbackData?: { recommendations: DataMappingRecommendation[] | null }
 ) {
+  const frontendFetch = useFrontendFetchWithAuth();
   const { data, error, isLoading } = useSWR(
     importerId
       ? [`${getHost()}/api/importer/${importerId}/mappings/recommendations`]
       : null,
-    ([url]) => fetchWithAuth(url).then((res) => res.json()),
+    ([url]) => frontendFetch(url).then((res) => res.json()),
     {
       refreshInterval: pollInterval,
       fallbackData,
diff --git a/app/src/lib/ImporterManager.ts b/app/src/lib/ImporterManager.ts
new file mode 100644
index 0000000..ecf4e8c
--- /dev/null
+++ b/app/src/lib/ImporterManager.ts
@@ -0,0 +1,146 @@
+import {
+  DataMapping,
+  DataMappingRecommendation,
+  ImporterConfig,
+  ImporterDto,
+  ImporterStatus,
+  SourceData,
+} from "@/app/api/importer/[slug]/ImporterDto";
+import { WorkflowClient } from "@temporalio/client";
+import { Db, MongoClient } from "mongodb";
+
+import { getMongoClient } from "./mongoClient";
+import { getTemporalWorkflowClient } from "./temporalClient";
+
+export class ImporterManager {
+  constructor(
+    private readonly workflowClient: WorkflowClient,
+    private readonly mongoClient: MongoClient
+  ) {}
+
+  public async getImporterDto(importerId: string) {
+    const handle = this.workflowClient.getHandle(importerId);
+    const [status, config] = await Promise.all([
+      (await handle.query("importer:status")) as ImporterStatus,
+      (await handle.query("importer:config")) as ImporterConfig,
+    ]);
+    const importerDto: ImporterDto = {
+      importerId,
+      config,
+      status,
+    };
+    return importerDto;
+  }
+
+  public async getMappingRecommendations(
+    importerId: string
+  ): Promise<DataMappingRecommendation[]> {
+    const handle = this.workflowClient.getHandle(importerId);
+    const workflowState = await handle.query<ImporterStatus>("importer:status");
+    if (workflowState.state === "closed") {
+      throw new Error("Importer is closed");
+    }
+    const recommendations = await handle.query<DataMappingRecommendation[]>(
+      "importer:data-mapping-recommendations"
+    );
+    return recommendations;
+  }
+
+  public async updateMappings(importerId: string, mappings: DataMapping[]) {
+    const handle = this.workflowClient.getHandle(importerId);
+    const workflowState = await handle.query<ImporterStatus>("importer:status");
+    if (workflowState.state === "closed") {
+      throw new Error("Importer is closed");
+    }
+    await handle.executeUpdate("importer:update-mapping", {
+      args: [{ mappings }],
+    });
+  }
+
+  public async closeImporter(importerId: string) {
+    const handle = this.workflowClient.getHandle(importerId);
+    await handle.signal("importer:close");
+  }
+
+  public async getRecords(
+    importerId: string,
+    page: number,
+    size: number
+  ): Promise<SourceData[]> {
+    const handle = this.workflowClient.getHandle(importerId);
+    const workflowState = await handle.query<ImporterStatus>("importer:status");
+    if (workflowState.state === "closed") {
+      throw new Error("Importer is closed");
+    }
+    const db = this.getDb(importerId);
+    const records = await db
+      .collection<SourceData>("data")
+      .find()
+      .sort({ __sourceRowId: 1 })
+      .skip(page * size)
+      .limit(size)
+      .toArray();
+    return records;
+  }
+
+  public async patchRecords(
+    importerId: string,
+    patches: { column: string; rowId: string; newValue: string }[]
+  ) {
+    const handle = this.workflowClient.getHandle(importerId);
+    const workflowState = await handle.query<ImporterStatus>("importer:status");
+    if (workflowState.state === "closed") {
+      throw new Error("Importer is closed");
+    }
+    const updateResult = await handle.executeUpdate("importer:update-record", {
+      args: [{ patches }],
+    });
+    return updateResult;
+  }
+
+  public async startImport(importerId: string) {
+    const handle = this.workflowClient.getHandle(importerId);
+    const workflowState = await handle.query<ImporterStatus>("importer:status");
+    if (workflowState.state === "closed") {
+      throw new Error("Importer is closed");
+    }
+    await handle.executeUpdate("importer:start-import");
+  }
+
+  public async addFile(
+    importerId: string,
+    fileReference: string,
+    fileFormat: string,
+    bucket: string
+  ) {
+    const handle = this.workflowClient.getHandle(importerId);
+    const workflowState = await handle.query<ImporterStatus>("importer:status");
+    if (workflowState.state === "closed") {
+      throw new Error("Importer is closed");
+    }
+    await handle.executeUpdate("importer:add-file", {
+      args: [
+        {
+          fileReference,
+          fileFormat,
+          bucket,
+        },
+      ],
+    });
+  }
+
+  private getDb(importerId: string): Db {
+    return this.mongoClient.db(importerId);
+  }
+}
+
+let importerManager: ImporterManager;
+
+export async function getImporterManager() {
+  if (!importerManager) {
+    const workflowClient = await getTemporalWorkflowClient();
+    const mongoClient = await getMongoClient();
+    importerManager = new ImporterManager(workflowClient, mongoClient);
+  }
+  return importerManager;
+}
diff --git a/app/src/lib/frontendFetch.ts b/app/src/lib/frontendFetch.ts
index 625667b..e071df5 100644
--- a/app/src/lib/frontendFetch.ts
+++ b/app/src/lib/frontendFetch.ts
@@ -1,9 +1,15 @@
-export async function fetchWithAuth(...args: Parameters<typeof fetch>) {
-  return await fetch(args[0], {
-    ...args[1],
-    headers: {
-      authorization: "Bearer " + process.env.NEXT_PUBLIC_FRONTEND_TOKEN,
-      ...args[1]?.headers,
-    },
-  });
+export function useFrontendFetchWithAuth() {
+  const baseUrl = undefined; // TODO get from context or so
+  return async (...args: Parameters<typeof fetch>) => {
+    const url = baseUrl
+      ? new URL(args[0] as string, baseUrl)
+      : (args[0] as string);
+    return await fetch(url, {
+      ...args[1],
+      headers: {
+        authorization: "Bearer " + process.env.NEXT_PUBLIC_FRONTEND_TOKEN,
+        ...args[1]?.headers,
+      },
+    });
+  };
 }
diff --git a/app/src/lib/mongoClient.ts b/app/src/lib/mongoClient.ts
index 65487e4..f808c3a 100644
--- a/app/src/lib/mongoClient.ts
+++ b/app/src/lib/mongoClient.ts
@@ -4,10 +4,15 @@ import { MongoClient } from "mongodb";
 let client: Promise<MongoClient>;
 
 export const getDb = async (dbName: string) => {
+  const client = await getMongoClient();
+  return client.db(dbName);
+};
+
+export const getMongoClient = async () => {
   if (!client) {
     client = new MongoClient(env.get("MONGO_URL").required().asString(), {
       appName: "nextjs",
     }).connect();
   }
-  return (await client).db(dbName);
+  return await client;
 };
diff --git a/app/src/lib/temporalClient.ts b/app/src/lib/temporalClient.ts
index 952a886..8010a4a 100644
--- a/app/src/lib/temporalClient.ts
+++ b/app/src/lib/temporalClient.ts
@@ -5,7 +5,6 @@ export const DEFAULT_TEMPORAL_QUEUE = "imports";
 let connection: Connection;
 
 export async function getTemporalWorkflowClient() {
-  // TODO get options from env
   if (!connection) {
     connection = await Connection.connect({
       address: env.get("TEMPORAL_ADDRESS").default("localhost:7233").asString(),
diff --git a/app/src/lib/utils.ts b/app/src/lib/utils.ts
index 9e0be58..be7eb6f 100644
--- a/app/src/lib/utils.ts
+++ b/app/src/lib/utils.ts
@@ -6,10 +6,11 @@ export function cn(...inputs: ClassValue[]) {
 }
 
 export function getHost(): string {
-  // this is needed because we use the api for ssr to. This is not really a good solution but works for now
-  // See https://github.com/vercel/next.js/discussions/48793 for the "correct" way
   const isServer = typeof window === "undefined";
-  const host = isServer ? "http://127.0.0.1:3000" : "";
+  if (isServer) {
+    throw new Error("getHost() should only be called on the client");
+  }
+  const host = "";
   return host;
 }