diff --git a/catalog/catalog.go b/catalog/catalog.go
index 281b8861..81bb4b5e 100644
--- a/catalog/catalog.go
+++ b/catalog/catalog.go
@@ -327,7 +327,7 @@ func (d *Directory) GetDataShapes(key *io.TimeBucketKey) (dsv []io.DataShape, er
 	return fi.GetDataShapes(), nil
 }
 
-func (d *Directory) AddFile(newYear int16) (finfo_p *io.TimeBucketInfo, err error) { //d should be a subdirectory
+func (d *Directory) AddFile(newYear int16) (finfo_p *io.TimeBucketInfo, err error) { // d should be a subdirectory
 	// Must be thread-safe for WRITE access
 	/*
 	 Adds a new primary storage file for the provided year to this directory
diff --git a/contrib/alpaca/config/config.go b/contrib/alpaca/config/config.go
index f0c43a41..0ec32b26 100644
--- a/contrib/alpaca/config/config.go
+++ b/contrib/alpaca/config/config.go
@@ -62,7 +62,7 @@ func flatten(lists ...[]string) []string {
 func prefixStrings(list []string, prefix string) []string {
 	res := make([]string, len(list))
 	for i, s := range list {
-		res[i] = string(prefix) + s
+		res[i] = prefix + s
 	}
 	return res
 }
diff --git a/contrib/alpacabkfeeder/README.md b/contrib/alpacabkfeeder/README.md
index 3627e481..2c3b6841 100644
--- a/contrib/alpacabkfeeder/README.md
+++ b/contrib/alpacabkfeeder/README.md
@@ -23,13 +23,30 @@ bgworkers:
         - NASDAQ
         # - NYSEARCA
         # - OTC
-      # time when the list of target symbols (tradable stocks) are updated every day.
+      # (optional) time when the list of target symbols (tradable stocks) are updated every day.
       # This config can be manually overridden by "ALPACA_BROKER_FEEDER_SYMBOLS_UPDATE_TIME" environmental variable.
-      symbols_update_time: "13:00:00" # (UTC). = every day at 08:00:00 (EST)
+      #symbols_update_time: "13:00:00" # (UTC). = every day at 08:00:00 (EST)
       # time when the historical data back-fill is run.
       # This config can be manually overridden by "ALPACA_BROKER_FEEDER_UPDATE_TIME" environmental variable.
       update_time: "13:30:00" # (UTC). = every day at 08:30:00 (EST)
-      # Alpava Broker API Feeder writes data to "{symbol}/{timeframe}/TICK" TimeBucketKey
+      # (optional) When stocks_json_url is specified, Alpaca Broker feeder retrieves data for only the stocks
+      # written in the json file.
+      # The example json file structure:
+      # {
+      #  "data": {
+      #    "AAPL": {...},
+      #    "ACN": {...},
+      #    "ADBE": {...}
+      #   }
+      # }
+      # In this case, Alpaca broker feeder gets "AAPL", "ACN", and "ADBE"'s data only.
+      # Any object under each symbol name is ignored.
+      stocks_json_url: "https://example.com/tradable_stocks.json"
+      # (optional) If the stocks_json file is authorized by basic auth,
+      # please specify "{user}:{pass}" (e.g. "john:mypassword").
+      # This config can be manually overridden by "ALPACA_BROKER_FEEDER_STOCKS_JSON_BASIC_AUTH"
+      stocks_json_basic_auth: "user:pass"
+      # Alpaca Broker API Feeder writes data to "{symbol}/{timeframe}/TICK" TimeBucketKey
       timeframe: "1Sec"
       # API Key ID and Secret for Alpaca Broker API
       # This config can be manually overridden by "ALPACA_BROKER_FEEDER_API_KEY_ID" and "ALPACA_BROKER_FEEDER_API_SECRET_KEY"
diff --git a/contrib/alpacabkfeeder/alpacav2.go b/contrib/alpacabkfeeder/alpacav2.go
index 376bd488..dfab64a9 100644
--- a/contrib/alpacabkfeeder/alpacav2.go
+++ b/contrib/alpacabkfeeder/alpacav2.go
@@ -66,10 +66,18 @@ func NewBgWorker(conf map[string]interface{}) (bgworker.BgWorker, error) {
 
 	ctx := context.Background()
 	// init symbols Manager to update symbols in the target exchanges
-	sm := symbols.NewJSONFileManager(&http.Client{Timeout: getJSONFileTimeout},
-		config.StocksJSONURL, config.StocksJSONBasicAuth,
-	)
+	var sm symbols.Manager
+	sm = symbols.NewManager(apiCli, config.Exchanges)
+	if config.StocksJSONURL != "" {
+		// use a remote JSON file instead of the config.Exchanges to list up the symbols
+		sm = symbols.NewJSONFileManager(&http.Client{Timeout: getJSONFileTimeout},
+			config.StocksJSONURL, config.StocksJSONBasicAuth,
+		)
+	}
 	sm.UpdateSymbols()
+	if config.SymbolsUpdateTime.IsZero() {
+		config.SymbolsUpdateTime = config.UpdateTime
+	}
 	timer.RunEveryDayAt(ctx, config.SymbolsUpdateTime, sm.UpdateSymbols)
 	log.Info("updated symbols using a remote json file.")
 
diff --git a/contrib/alpacabkfeeder/api/client.go b/contrib/alpacabkfeeder/api/client.go
index be1fbef5..5748b888 100644
--- a/contrib/alpacabkfeeder/api/client.go
+++ b/contrib/alpacabkfeeder/api/client.go
@@ -8,7 +8,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
-	"strconv"
+	"sort"
 	"strings"
 	"time"
 
@@ -149,44 +149,125 @@ func (c *Client) GetSnapshots(symbols []string) (map[string]*Snapshot, error) {
 	return snapshots, nil
 }
 
-// ListBars returns a list of bar lists corresponding to the provided
-// symbol list, and filtered by the provided parameters.
-func (c *Client) ListBars(symbols []string, opts v1.ListBarParams) (map[string][]v1.Bar, error) {
-	vals := url.Values{}
-	vals.Add("symbols", strings.Join(symbols, ","))
-
-	if opts.Timeframe == "" {
-		return nil, fmt.Errorf("timeframe is required for the bars endpoint")
+// GetMultiBars returns bars for the given symbols.
+func (c *Client) GetMultiBars(
+	symbols []string, params GetBarsParams,
+) (map[string][]Bar, error) {
+	bars := make(map[string][]Bar, len(symbols))
+	for item := range c.GetMultiBarsAsync(symbols, params) {
+		if err := item.Error; err != nil {
+			return nil, err
+		}
+		bars[item.Symbol] = append(bars[item.Symbol], item.Bar)
 	}
+	return bars, nil
+}
 
-	if opts.StartDt != nil {
-		vals.Set("start", opts.StartDt.Format(time.RFC3339))
-	}
+// GetMultiBarsAsync returns a channel that will be populated with the bars for the requested symbols.
+func (c *Client) GetMultiBarsAsync(symbols []string, params GetBarsParams) <-chan MultiBarItem {
+	ch := make(chan MultiBarItem)
 
-	if opts.EndDt != nil {
-		vals.Set("end", opts.EndDt.Format(time.RFC3339))
-	}
+	go func() {
+		defer close(ch)
 
-	if opts.Limit != nil {
-		vals.Set("limit", strconv.FormatInt(int64(*opts.Limit), 10))
-	}
+		u, err := url.Parse(fmt.Sprintf("%s/v2/stocks/bars", dataURL))
+		if err != nil {
+			ch <- MultiBarItem{Error: err}
+			return
+		}
 
-	u, err := url.Parse(fmt.Sprintf("%s/v1/bars/%s?%v", dataURL, opts.Timeframe, vals.Encode()))
-	if err != nil {
-		return nil, err
+		q := u.Query()
+		q.Set("symbols", strings.Join(symbols, ","))
+		setQueryBarParams(q, params, "")
+
+		received := 0
+		for params.TotalLimit == 0 || received < params.TotalLimit {
+			setQueryLimit(q, params.TotalLimit, params.PageLimit, received)
+			u.RawQuery = q.Encode()
+
+			resp, err := c.get(u)
+			if err != nil {
+				ch <- MultiBarItem{Error: err}
+				return
+			}
+
+			var barResp multiBarResponse
+			if err = unmarshal(resp, &barResp); err != nil {
+				ch <- MultiBarItem{Error: err}
+				return
+			}
+
+			sortedSymbols := make([]string, 0, len(barResp.Bars))
+			for symbol := range barResp.Bars {
+				sortedSymbols = append(sortedSymbols, symbol)
+			}
+			sort.Strings(sortedSymbols)
+
+			for _, symbol := range sortedSymbols {
+				bars := barResp.Bars[symbol]
+				for _, bar := range bars {
+					ch <- MultiBarItem{Symbol: symbol, Bar: bar}
+				}
+				received += len(bars)
+			}
+			if barResp.NextPageToken == nil {
+				return
+			}
+			q.Set("page_token", *barResp.NextPageToken)
+		}
+	}()
+
+	return ch
+}
+
+func setQueryBarParams(q url.Values, params GetBarsParams, feed string) {
+	setBaseQuery(q, params.Start, params.End, params.Feed, feed)
+	adjustment := Raw
+	if params.Adjustment != "" {
+		adjustment = params.Adjustment
 	}
+	q.Set("adjustment", string(adjustment))
+	timeframe := OneDay
+	if params.TimeFrame.N != 0 {
+		timeframe = params.TimeFrame
+	}
+	q.Set("timeframe", timeframe.String())
+}
 
-	resp, err := c.get(u)
-	if err != nil {
-		return nil, err
+func setBaseQuery(q url.Values, start, end time.Time, feed, defaultFeed string) {
+	if !start.IsZero() {
+		q.Set("start", start.Format(time.RFC3339))
+	}
+	if !end.IsZero() {
+		q.Set("end", end.Format(time.RFC3339))
+	}
+	if feed != "" {
+		q.Set("feed", feed)
+	} else {
+		if defaultFeed != "" {
+			q.Set("feed", feed)
+		}
 	}
-	var bars map[string][]v1.Bar
+}
 
-	if err = unmarshal(resp, &bars); err != nil {
-		return nil, err
+func setQueryLimit(q url.Values, totalLimit int, pageLimit int, received int) {
+	limit := 0 // use server side default if unset
+	if pageLimit != 0 {
+		limit = pageLimit
+	}
+	if totalLimit != 0 {
+		remaining := totalLimit - received
+		if remaining <= 0 { // this should never happen
+			return
+		}
+		if (limit == 0 || limit > remaining) && remaining <= v2MaxLimit {
+			limit = remaining
+		}
 	}
 
-	return bars, nil
+	if limit != 0 {
+		q.Set("limit", fmt.Sprintf("%d", limit))
+	}
 }
 
 // ListAssets returns the list of assets, filtered by
diff --git a/contrib/alpacabkfeeder/api/entities.go b/contrib/alpacabkfeeder/api/entities.go
index 2c54a4ea..b196b986 100644
--- a/contrib/alpacabkfeeder/api/entities.go
+++ b/contrib/alpacabkfeeder/api/entities.go
@@ -1,6 +1,9 @@
 package api
 
-import "time"
+import (
+	"fmt"
+	"time"
+)
 
 // Trade is a stock trade that happened on the market.
 type Trade struct {
@@ -26,14 +29,28 @@ type Quote struct {
 	Tape        string    `json:"z"`
 }
 
-// Bar is an aggregate of trades.
+// Bar is an aggregate of trades
 type Bar struct {
-	Open      float64   `json:"o"`
-	High      float64   `json:"h"`
-	Low       float64   `json:"l"`
-	Close     float64   `json:"c"`
-	Volume    uint64    `json:"v"`
-	Timestamp time.Time `json:"t"`
+	Timestamp  time.Time `json:"t"`
+	Open       float64   `json:"o"`
+	High       float64   `json:"h"`
+	Low        float64   `json:"l"`
+	Close      float64   `json:"c"`
+	Volume     uint64    `json:"v"`
+	TradeCount uint64    `json:"n"`
+	VWAP       float64   `json:"vw"`
+}
+
+// MultiBarItem contains a single bar for a symbol or an error
+type MultiBarItem struct {
+	Symbol string
+	Bar    Bar
+	Error  error
+}
+
+type multiBarResponse struct {
+	NextPageToken *string          `json:"next_page_token"`
+	Bars          map[string][]Bar `json:"bars"`
 }
 
 // Snapshot is a snapshot of a symbol.
@@ -44,3 +61,67 @@ type Snapshot struct {
 	DailyBar     *Bar   `json:"dailyBar"`
 	PrevDailyBar *Bar   `json:"prevDailyBar"`
 }
+
+// GetBarsParams contains optional parameters for getting bars
+type GetBarsParams struct {
+	// TimeFrame is the aggregation size of the bars
+	TimeFrame TimeFrame
+	// Adjustment tells if the bars should be adjusted for corporate actions
+	Adjustment Adjustment
+	// Start is the inclusive beginning of the interval
+	Start time.Time
+	// End is the inclusive end of the interval
+	End time.Time
+	// TotalLimit is the limit of the total number of the returned bars.
+	// If missing, all bars between start end end will be returned.
+	TotalLimit int
+	// PageLimit is the pagination size. If empty, the default page size will be used.
+	PageLimit int
+	// Feed is the source of the data: sip or iex.
+	// If provided, it overrides the client's Feed option.
+	Feed string
+}
+
+// TimeFrameUnite is the base unit of the timeframe.
+type TimeFrameUnit string
+
+// List of timeframe units
+const (
+	Min  TimeFrameUnit = "Min"
+	Hour TimeFrameUnit = "Hour"
+	Day  TimeFrameUnit = "Day"
+)
+
+// TimeFrame is the resolution of the bars
+type TimeFrame struct {
+	N    int
+	Unit TimeFrameUnit
+}
+
+func NewTimeFrame(n int, unit TimeFrameUnit) TimeFrame {
+	return TimeFrame{
+		N:    n,
+		Unit: unit,
+	}
+}
+
+func (tf TimeFrame) String() string {
+	return fmt.Sprintf("%d%s", tf.N, tf.Unit)
+}
+
+var (
+	OneMin  TimeFrame = NewTimeFrame(1, Min)
+	OneHour TimeFrame = NewTimeFrame(1, Hour)
+	OneDay  TimeFrame = NewTimeFrame(1, Day)
+)
+
+// Adjustment specifies the corporate action adjustment(s) for the bars
+type Adjustment string
+
+// List of adjustments
+const (
+	Raw      Adjustment = "raw"
+	Split    Adjustment = "split"
+	Dividend Adjustment = "dividend"
+	All      Adjustment = "all"
+)
diff --git a/contrib/alpacabkfeeder/api/v1/entities.go b/contrib/alpacabkfeeder/api/v1/entities.go
index 3b82e5a2..d4dd571b 100644
--- a/contrib/alpacabkfeeder/api/v1/entities.go
+++ b/contrib/alpacabkfeeder/api/v1/entities.go
@@ -1,7 +1,5 @@
 package v1
 
-import "time"
-
 type Asset struct {
 	ID           string `json:"id"`
 	Name         string `json:"name"`
@@ -10,7 +8,7 @@ type Asset struct {
 	Symbol       string `json:"symbol"`
 	Status       string `json:"status"`
 	Tradable     bool   `json:"tradable"`
-	Marginal   bool   `json:"marginal"`
+	Marginal     bool   `json:"marginal"`
 	Shortable    bool   `json:"shortable"`
 	EasyToBorrow bool   `json:"easy_to_borrow"`
 }
@@ -23,10 +21,3 @@ type Bar struct {
 	Close  float32 `json:"c"`
 	Volume int32   `json:"v"`
 }
-
-type ListBarParams struct {
-	Timeframe string     `url:"timeframe,omitempty"`
-	StartDt   *time.Time `url:"start_dt,omitempty"`
-	EndDt     *time.Time `url:"end_dt,omitempty"`
-	Limit     *int       `url:"limit,omitempty"`
-}
diff --git a/contrib/alpacabkfeeder/feed/backfill.go b/contrib/alpacabkfeeder/feed/backfill.go
index 7a294754..49c36a4a 100644
--- a/contrib/alpacabkfeeder/feed/backfill.go
+++ b/contrib/alpacabkfeeder/feed/backfill.go
@@ -3,32 +3,33 @@ package feed
 import (
 	"time"
 
-	v1 "github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/api/v1"
+
+	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/api"
 	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/symbols"
 	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/writer"
 	"github.com/alpacahq/marketstore/v4/utils/log"
 )
 
-const backfillTimeframe = "1D"
+var backfillTimeframe = api.OneDay
 
 // Backfill aggregates daily chart data using Alpava v2 API and store it to marketstore.
 type Backfill struct {
 	symbolManager    symbols.Manager
-	apiClient        ListBarsAPIClient
+	apiClient        GetMultiBarsAPIClient
 	barWriter        writer.BarWriter
 	since            time.Time
 	maxBarsPerReq    int
 	maxSymbolsPerReq int
 }
 
-type ListBarsAPIClient interface {
-	ListBars(symbols []string, opts v1.ListBarParams) (map[string][]v1.Bar, error)
+type GetMultiBarsAPIClient interface {
+	GetMultiBars(symbols []string, params api.GetBarsParams) (map[string][]api.Bar, error)
 }
 
 // NewBackfill initializes the module to backfill the historical daily chart data to marketstore.
 // Alpaca API spec: maxBarsPerRequest: 1000 bars per symbol per request at maximum
 // Alpaca API spec: maxSymbolsPerRequest: 100 symbols per request at maximum.
-func NewBackfill(symbolManager symbols.Manager, apiClient ListBarsAPIClient, barWriter writer.BarWriter,
+func NewBackfill(symbolManager symbols.Manager, apiClient GetMultiBarsAPIClient, barWriter writer.BarWriter,
 	since time.Time, maxBarsPerReq, maxSymbolsPerReq int,
 ) *Backfill {
 	return &Backfill{
@@ -48,20 +49,20 @@ func (b *Backfill) UpdateSymbols() {
 	for idx := range pageIndex(len(allSymbols), b.maxSymbolsPerReq) {
 		for dateRange := range datePageIndex(b.since, until, b.maxBarsPerReq) {
 			// fmt.Printf("start=%v, end=%v, symbols=%v\n", dateRange.From, dateRange.To, allSymbols[idx.From:idx.To])
-			params := v1.ListBarParams{
-				Timeframe: backfillTimeframe,
-				StartDt:   time230000utc(dateRange.From),
-				EndDt:     time230000utc(dateRange.To),
-				Limit:     &b.maxBarsPerReq,
+			params := api.GetBarsParams{
+				TimeFrame: backfillTimeframe,
+				Start:     time230000utc(dateRange.From),
+				End:       maxPast16min(time230000utc(dateRange.To)),
+				PageLimit: b.maxBarsPerReq,
 			}
 
 			// get data
-			symbolBarsMap, err := b.apiClient.ListBars(allSymbols[idx.From:idx.To], params)
+			symbolBarsMap, err := b.apiClient.GetMultiBars(allSymbols[idx.From:idx.To], params)
 			if err != nil {
-				log.Error("Alpaca Broker ListBars API call error. Err=%v", err)
+				log.Error("Alpaca MarketData GetMultiBars API call error. params=%v, Err=%v", params, err)
 				return
 			}
-			log.Info("Alpaca ListBars API call: From=%v, To=%v, symbols=%v",
+			log.Info("Alpaca GetMultiBars API call: From=%v, To=%v, symbols=%v",
 				dateRange.From, dateRange.To, allSymbols[idx.From:idx.To],
 			)
 
@@ -79,16 +80,28 @@ func (b *Backfill) UpdateSymbols() {
 	log.Info("[Alpaca Broker Feeder] daily chart backfill is successfully done.")
 }
 
-// Alpaca ListBars API returns daily chart data based on US time.
+// Alpaca GetMultiBars API returns daily chart data based on US time.
 // e.g. When 1D bar is requested with time.Date(2021, 12,1,0,0,0,0,time.UTC),
 // the API returns a daily chart for 2021-11-30 because 2021-12-01 00:00:00 UTC is 2021-11-30 19:00:00 EST.
 // So it's safe to always provide yyyy-mm-dd 23:00:00 UTC to the API when daily chart is necessary
 // because it can be considered that the market for the day is already closed at 23:00:00 UTC
 // regardless of the US timezones (EST, EDT).
-func time230000utc(time2 time.Time) *time.Time {
+func time230000utc(time2 time.Time) time.Time {
 	y, m, d := time2.Date()
 	t := time.Date(y, m, d, 23, 0, 0, 0, time.UTC)
-	return &t
+	return t
+}
+
+// Alpaca API doesn't allow querying historical bars data from the past 15 minutes depending on the subscription.
+// https://alpaca.markets/docs/market-data/#subscription-plans
+// maxPast16min returns the specified time or the time 16 minutes ago from now,
+// to avoid "your subscription does not permit querying data from the past 15 minutes" error.
+func maxPast16min(time2 time.Time) time.Time {
+	past16min := time.Now().Add(-16 * time.Minute)
+	if time2.After(past16min) {
+		return past16min
+	}
+	return time2
 }
 
 // utilities for pagination.
diff --git a/contrib/alpacabkfeeder/feed/backfill_test.go b/contrib/alpacabkfeeder/feed/backfill_test.go
index f828510a..3edfc07c 100644
--- a/contrib/alpacabkfeeder/feed/backfill_test.go
+++ b/contrib/alpacabkfeeder/feed/backfill_test.go
@@ -7,7 +7,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/assert"
 
-	v1 "github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/api/v1"
+	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/api"
 	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/feed"
 	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/internal"
 	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/writer"
@@ -22,46 +22,46 @@ var (
 	d3                     = time.Date(d3Year, d3Month, d3Day, 0, 0, 0, 0, time.UTC)
 )
 
-var testBars = map[string][]v1.Bar{
+var testBars = map[string][]api.Bar{
 	"AAPL": {
-		{Time: d3.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 1},
-		{Time: d2.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 2},
-		{Time: d.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 3},
+		{Timestamp: d3, Open: 0, High: 0, Low: 0, Close: 0, Volume: 1},
+		{Timestamp: d2, Open: 0, High: 0, Low: 0, Close: 0, Volume: 2},
+		{Timestamp: d, Open: 0, High: 0, Low: 0, Close: 0, Volume: 3},
 	},
 	"AMZN": {
-		{Time: d3.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 4},
-		{Time: d2.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 5},
-		{Time: d.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 6},
+		{Timestamp: d3, Open: 0, High: 0, Low: 0, Close: 0, Volume: 4},
+		{Timestamp: d2, Open: 0, High: 0, Low: 0, Close: 0, Volume: 5},
+		{Timestamp: d, Open: 0, High: 0, Low: 0, Close: 0, Volume: 6},
 	},
 	"FB": {
-		{Time: d3.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 7},
-		{Time: d2.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 8},
-		{Time: d.Unix(), Open: 0, High: 0, Low: 0, Close: 0, Volume: 9},
+		{Timestamp: d3, Open: 0, High: 0, Low: 0, Close: 0, Volume: 7},
+		{Timestamp: d2, Open: 0, High: 0, Low: 0, Close: 0, Volume: 8},
+		{Timestamp: d, Open: 0, High: 0, Low: 0, Close: 0, Volume: 9},
 	},
 }
 
 const errorSymbol = "ERROR"
 
 type MockErrorAPIClient struct {
-	testBars map[string][]v1.Bar
+	testBars map[string][]api.Bar
 	internal.MockAPIClient
 }
 
-// ListBars returns an error if symbol:"ERROR" is included, but returns data to other symbols.
-func (mac *MockErrorAPIClient) ListBars(symbols []string, opts v1.ListBarParams) (map[string][]v1.Bar, error) {
-	ret := make(map[string][]v1.Bar)
+// GetMultiBars returns an error if symbol:"ERROR" is included, but returns data to other symbols.
+func (mac *MockErrorAPIClient) GetMultiBars(symbols []string, opts api.GetBarsParams) (map[string][]api.Bar, error) {
+	ret := make(map[string][]api.Bar)
 	for _, symbl := range symbols {
 		if symbl == errorSymbol {
 			return nil, errors.New("error")
 		}
 		if bars, found := mac.testBars[symbl]; found {
-			barPage := make([]v1.Bar, 0)
+			barPage := make([]api.Bar, 0)
 
 			// filter by time
 			for _, bar := range bars {
-				barTime := time.Unix(bar.Time, 0).UTC().Truncate(24 * time.Hour) // 00:00:00 of the bar time
-				startDt := opts.StartDt.UTC().Truncate(24 * time.Hour)
-				endDt := opts.EndDt.UTC().Truncate(24 * time.Hour)
+				barTime := time.Unix(bar.Timestamp.Unix(), 0).UTC().Truncate(24 * time.Hour) // 00:00:00 of the bar time
+				startDt := opts.Start.UTC().Truncate(24 * time.Hour)
+				endDt := opts.End.UTC().Truncate(24 * time.Hour)
 
 				if barTime.Equal(startDt) || (barTime.After(startDt) && barTime.Before(startDt)) || barTime.Equal(endDt) {
 					barPage = append(barPage, bar)
@@ -79,7 +79,7 @@ type MockBarWriter struct {
 	WriteCount int
 }
 
-func (mbw *MockBarWriter) Write(symbol string, bars []v1.Bar) error {
+func (mbw *MockBarWriter) Write(symbol string, bars []api.Bar) error {
 	// in order to assert the number of written bars in the test
 	mbw.WriteCount += len(bars)
 	return nil
@@ -91,7 +91,7 @@ func TestBackfill_UpdateSymbols(t *testing.T) {
 	tests := []struct {
 		name                string
 		smbls               []string
-		testBars            map[string][]v1.Bar
+		testBars            map[string][]api.Bar
 		barWriter           writer.BarWriter
 		maxSymbolsPerReq    int
 		maxBarsPerReq       int
diff --git a/contrib/alpacabkfeeder/internal/mocks.go b/contrib/alpacabkfeeder/internal/mocks.go
index 9047118d..5a32679b 100644
--- a/contrib/alpacabkfeeder/internal/mocks.go
+++ b/contrib/alpacabkfeeder/internal/mocks.go
@@ -18,6 +18,9 @@ func (msm MockSymbolsManager) GetAllSymbols() []string {
 	return msm.Symbols
 }
 
+// UpdateSymbols does nothing.
+func (msm MockSymbolsManager) UpdateSymbols() {}
+
 // MockAPIClient is a no-op API client.
 type MockAPIClient struct{}
 
@@ -31,9 +34,9 @@ func (mac *MockAPIClient) ListAssets(status *string) ([]v1.Asset, error) {
 	return []v1.Asset{}, nil
 }
 
-// ListBars returns an empty api response.
-func (mac *MockAPIClient) ListBars(symbols []string, opts v1.ListBarParams) (map[string][]v1.Bar, error) {
-	return map[string][]v1.Bar{}, nil
+// GetMultiBars returns an empty api response.
+func (mac *MockAPIClient) GetMultiBars(symbols []string, opts api.GetBarsParams) (map[string][]api.Bar, error) {
+	return map[string][]api.Bar{}, nil
 }
 
 // MockTimeChecker always returns Open.
diff --git a/contrib/alpacabkfeeder/symbols/manager.go b/contrib/alpacabkfeeder/symbols/manager.go
index 30669389..193d2ea5 100644
--- a/contrib/alpacabkfeeder/symbols/manager.go
+++ b/contrib/alpacabkfeeder/symbols/manager.go
@@ -21,6 +21,7 @@ var (
 // so target symbols should be updated periodically.
 type Manager interface {
 	GetAllSymbols() []string
+	UpdateSymbols()
 }
 
 type APIClient interface {
diff --git a/contrib/alpacabkfeeder/writer/bar_writer.go b/contrib/alpacabkfeeder/writer/bar_writer.go
index 6396379f..69dc19c2 100644
--- a/contrib/alpacabkfeeder/writer/bar_writer.go
+++ b/contrib/alpacabkfeeder/writer/bar_writer.go
@@ -6,14 +6,14 @@ import (
 
 	"github.com/pkg/errors"
 
-	v1 "github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/api/v1"
+	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/api"
 	"github.com/alpacahq/marketstore/v4/utils/io"
 	"github.com/alpacahq/marketstore/v4/utils/log"
 )
 
 // BarWriter is an interface to write chart data to the marketstore.
 type BarWriter interface {
-	Write(symbol string, bars []v1.Bar) error
+	Write(symbol string, bars []api.Bar) error
 }
 
 // BarWriterImpl is an implementation of the BarWriter interface.
@@ -24,8 +24,8 @@ type BarWriterImpl struct {
 	Timezone *time.Location
 }
 
-// Write converts the Response of the ListBars API to a ColumnSeriesMap and write it to the local marketstore server.
-func (b BarWriterImpl) Write(symbol string, bars []v1.Bar) error {
+// Write converts the Response of the GetMultiBars API to a ColumnSeriesMap and write it to the local marketstore server.
+func (b BarWriterImpl) Write(symbol string, bars []api.Bar) error {
 	// convert Bar Data to CSM (ColumnSeriesMap)
 	csm := b.convertToCSM(symbol, bars)
 
@@ -39,13 +39,13 @@ func (b BarWriterImpl) Write(symbol string, bars []v1.Bar) error {
 	return nil
 }
 
-func (b *BarWriterImpl) convertToCSM(symbol string, bars []v1.Bar) io.ColumnSeriesMap {
+func (b *BarWriterImpl) convertToCSM(symbol string, bars []api.Bar) io.ColumnSeriesMap {
 	epochs := make([]int64, len(bars))
 	opens := make([]float32, len(bars))
 	closes := make([]float32, len(bars))
 	highs := make([]float32, len(bars))
 	lows := make([]float32, len(bars))
-	volumes := make([]int32, len(bars))
+	volumes := make([]uint64, len(bars))
 	csm := io.NewColumnSeriesMap()
 
 	for i := range bars {
@@ -67,11 +67,11 @@ func (b *BarWriterImpl) convertToCSM(symbol string, bars []v1.Bar) io.ColumnSeri
 
 		// Start time of each bar is used for "epoch"
 		// to align with the 1-day chart backfill. ("00:00:00"(starting time of a day) is used for epoch)
-		epochs[i] = bars[i].Time
-		opens[i] = bars[i].Open
-		closes[i] = bars[i].Close
-		highs[i] = bars[i].High
-		lows[i] = bars[i].Low
+		epochs[i] = bars[i].Timestamp.Unix()
+		opens[i] = float32(bars[i].Open)
+		closes[i] = float32(bars[i].Close)
+		highs[i] = float32(bars[i].High)
+		lows[i] = float32(bars[i].Low)
 		volumes[i] = bars[i].Volume
 	}
 
@@ -87,7 +87,7 @@ func (b *BarWriterImpl) convertToCSM(symbol string, bars []v1.Bar) io.ColumnSeri
 	return csm
 }
 
-func (b BarWriterImpl) newColumnSeries(epochs []int64, opens, closes, highs, lows []float32, volumes []int32,
+func (b BarWriterImpl) newColumnSeries(epochs []int64, opens, closes, highs, lows []float32, volumes []uint64,
 ) *io.ColumnSeries {
 	cs := io.NewColumnSeries()
 	cs.AddColumn("Epoch", epochs)
diff --git a/contrib/alpacabkfeeder/writer/bar_writer_test.go b/contrib/alpacabkfeeder/writer/bar_writer_test.go
index 51bfa03e..3e5ae803 100644
--- a/contrib/alpacabkfeeder/writer/bar_writer_test.go
+++ b/contrib/alpacabkfeeder/writer/bar_writer_test.go
@@ -4,7 +4,7 @@ import (
 	"testing"
 	"time"
 
-	v1 "github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/api/v1"
+	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/api"
 	"github.com/alpacahq/marketstore/v4/contrib/alpacabkfeeder/internal"
 	"github.com/alpacahq/marketstore/v4/utils/io"
 )
@@ -26,22 +26,22 @@ func TestBarWriterImpl_Write(t *testing.T) {
 
 	// 2 bar data
 	symbol := "1234"
-	bars := []v1.Bar{
+	bars := []api.Bar{
 		{
-			Time:   barTimestamp1.Unix(),
-			Open:   12.3,
-			Close:  45.6,
-			High:   78.9,
-			Low:    0.12,
-			Volume: 100,
+			Timestamp: barTimestamp1,
+			Open:      12.3,
+			Close:     45.6,
+			High:      78.9,
+			Low:       0.12,
+			Volume:    100,
 		},
 		{
-			Time:   barTimestamp2.Unix(),
-			Open:   1.2,
-			Close:  3.4,
-			High:   5.6,
-			Low:    7.8,
-			Volume: 100,
+			Timestamp: barTimestamp2,
+			Open:      1.2,
+			Close:     3.4,
+			High:      5.6,
+			Low:       7.8,
+			Volume:    100,
 		},
 	}
 
diff --git a/contrib/alpacabkfeeder/writer/snapshot_writer.go b/contrib/alpacabkfeeder/writer/snapshot_writer.go
index 02528c0d..84ec6c5f 100644
--- a/contrib/alpacabkfeeder/writer/snapshot_writer.go
+++ b/contrib/alpacabkfeeder/writer/snapshot_writer.go
@@ -80,30 +80,30 @@ func (q SnapshotWriterImpl) newColumnSeries(epoch int64, ss *api.Snapshot) *io.C
 	cs := io.NewColumnSeries()
 	cs.AddColumn("Epoch", []int64{epoch})
 	cs.AddColumn("QuoteTimestamp", []int64{ss.LatestQuote.Timestamp.In(q.Timezone).Unix()})
-	cs.AddColumn("Ask", []float64{ss.LatestQuote.AskPrice})
+	cs.AddColumn("Ask", []float32{float32(ss.LatestQuote.AskPrice)})
 	cs.AddColumn("AskSize", []uint32{ss.LatestQuote.AskSize})
-	cs.AddColumn("Bid", []float64{ss.LatestQuote.BidPrice})
+	cs.AddColumn("Bid", []float32{float32(ss.LatestQuote.BidPrice)})
 	cs.AddColumn("BidSize", []uint32{ss.LatestQuote.BidSize})
 	cs.AddColumn("TradeTimestamp", []int64{ss.LatestTrade.Timestamp.In(q.Timezone).Unix()})
-	cs.AddColumn("Price", []float64{ss.LatestTrade.Price})
+	cs.AddColumn("Price", []float32{float32(ss.LatestTrade.Price)})
 	cs.AddColumn("Size", []uint32{ss.LatestTrade.Size})
 	cs.AddColumn("DailyTimestamp", []int64{ss.DailyBar.Timestamp.In(q.Timezone).Unix()})
-	cs.AddColumn("Open", []float64{ss.DailyBar.Open})
-	cs.AddColumn("High", []float64{ss.DailyBar.High})
-	cs.AddColumn("Low", []float64{ss.DailyBar.Low})
-	cs.AddColumn("Close", []float64{ss.DailyBar.Close})
+	cs.AddColumn("Open", []float32{float32(ss.DailyBar.Open)})
+	cs.AddColumn("High", []float32{float32(ss.DailyBar.High)})
+	cs.AddColumn("Low", []float32{float32(ss.DailyBar.Low)})
+	cs.AddColumn("Close", []float32{float32(ss.DailyBar.Close)})
 	cs.AddColumn("Volume", []uint64{ss.DailyBar.Volume})
 	cs.AddColumn("MinuteTimestamp", []int64{ss.MinuteBar.Timestamp.In(q.Timezone).Unix()})
-	cs.AddColumn("MinuteOpen", []float64{ss.MinuteBar.Open})
-	cs.AddColumn("MinuteHigh", []float64{ss.MinuteBar.High})
-	cs.AddColumn("MinuteLow", []float64{ss.MinuteBar.Low})
-	cs.AddColumn("MinuteClose", []float64{ss.MinuteBar.Close})
+	cs.AddColumn("MinuteOpen", []float32{float32(ss.MinuteBar.Open)})
+	cs.AddColumn("MinuteHigh", []float32{float32(ss.MinuteBar.High)})
+	cs.AddColumn("MinuteLow", []float32{float32(ss.MinuteBar.Low)})
+	cs.AddColumn("MinuteClose", []float32{float32(ss.MinuteBar.Close)})
 	cs.AddColumn("MinuteVolume", []uint64{ss.MinuteBar.Volume})
 	cs.AddColumn("PreviousTimestamp", []int64{ss.PrevDailyBar.Timestamp.In(q.Timezone).Unix()})
-	cs.AddColumn("PreviousOpen", []float64{ss.PrevDailyBar.Open})
-	cs.AddColumn("PreviousHigh", []float64{ss.PrevDailyBar.High})
-	cs.AddColumn("PreviousLow", []float64{ss.PrevDailyBar.Low})
-	cs.AddColumn("PreviousClose", []float64{ss.PrevDailyBar.Close})
+	cs.AddColumn("PreviousOpen", []float32{float32(ss.PrevDailyBar.Open)})
+	cs.AddColumn("PreviousHigh", []float32{float32(ss.PrevDailyBar.High)})
+	cs.AddColumn("PreviousLow", []float32{float32(ss.PrevDailyBar.Low)})
+	cs.AddColumn("PreviousClose", []float32{float32(ss.PrevDailyBar.Close)})
 	cs.AddColumn("PreviousVolume", []uint64{ss.PrevDailyBar.Volume})
 	return cs
 }
diff --git a/contrib/alpacabkfeeder/writer/snapshot_writer_test.go b/contrib/alpacabkfeeder/writer/snapshot_writer_test.go
index 1829e6f8..ca3bd102 100644
--- a/contrib/alpacabkfeeder/writer/snapshot_writer_test.go
+++ b/contrib/alpacabkfeeder/writer/snapshot_writer_test.go
@@ -93,30 +93,30 @@ func TestSnapshotWriterImpl_Write(t *testing.T) {
 			wantCSMDataShapes: []io.DataShape{
 				{Name: "Epoch", Type: io.INT64},
 				{Name: "QuoteTimestamp", Type: io.INT64},
-				{Name: "Ask", Type: io.FLOAT64},
+				{Name: "Ask", Type: io.FLOAT32},
 				{Name: "AskSize", Type: io.UINT32},
-				{Name: "Bid", Type: io.FLOAT64},
+				{Name: "Bid", Type: io.FLOAT32},
 				{Name: "BidSize", Type: io.UINT32},
 				{Name: "TradeTimestamp", Type: io.INT64},
-				{Name: "Price", Type: io.FLOAT64},
+				{Name: "Price", Type: io.FLOAT32},
 				{Name: "Size", Type: io.UINT32},
 				{Name: "DailyTimestamp", Type: io.INT64},
-				{Name: "Open", Type: io.FLOAT64},
-				{Name: "High", Type: io.FLOAT64},
-				{Name: "Low", Type: io.FLOAT64},
-				{Name: "Close", Type: io.FLOAT64},
+				{Name: "Open", Type: io.FLOAT32},
+				{Name: "High", Type: io.FLOAT32},
+				{Name: "Low", Type: io.FLOAT32},
+				{Name: "Close", Type: io.FLOAT32},
 				{Name: "Volume", Type: io.UINT64},
 				{Name: "MinuteTimestamp", Type: io.INT64},
-				{Name: "MinuteOpen", Type: io.FLOAT64},
-				{Name: "MinuteHigh", Type: io.FLOAT64},
-				{Name: "MinuteLow", Type: io.FLOAT64},
-				{Name: "MinuteClose", Type: io.FLOAT64},
+				{Name: "MinuteOpen", Type: io.FLOAT32},
+				{Name: "MinuteHigh", Type: io.FLOAT32},
+				{Name: "MinuteLow", Type: io.FLOAT32},
+				{Name: "MinuteClose", Type: io.FLOAT32},
 				{Name: "MinuteVolume", Type: io.UINT64},
 				{Name: "PreviousTimestamp", Type: io.INT64},
-				{Name: "PreviousOpen", Type: io.FLOAT64},
-				{Name: "PreviousHigh", Type: io.FLOAT64},
-				{Name: "PreviousLow", Type: io.FLOAT64},
-				{Name: "PreviousClose", Type: io.FLOAT64},
+				{Name: "PreviousOpen", Type: io.FLOAT32},
+				{Name: "PreviousHigh", Type: io.FLOAT32},
+				{Name: "PreviousLow", Type: io.FLOAT32},
+				{Name: "PreviousClose", Type: io.FLOAT32},
 				{Name: "PreviousVolume", Type: io.UINT64},
 			},
 			wantCSMLen: 1,
diff --git a/contrib/gdaxfeeder/gdaxfeeder.go b/contrib/gdaxfeeder/gdaxfeeder.go
index 7a0e6d10..09f1c6b1 100644
--- a/contrib/gdaxfeeder/gdaxfeeder.go
+++ b/contrib/gdaxfeeder/gdaxfeeder.go
@@ -220,10 +220,10 @@ func (gd *GdaxFetcher) Run() {
 					lastTime = rate.Time
 				}
 				epoch = append(epoch, rate.Time.Unix())
-				open = append(open, float64(rate.Open))
-				high = append(high, float64(rate.High))
-				low = append(low, float64(rate.Low))
-				clos = append(clos, float64(rate.Close))
+				open = append(open, rate.Open)
+				high = append(high, rate.High)
+				low = append(low, rate.Low)
+				clos = append(clos, rate.Close)
 				volume = append(volume, rate.Volume)
 			}
 			cs := io.NewColumnSeries()
diff --git a/utils/io/coercecolumn.go b/utils/io/coercecolumn.go
index c8e476ac..6469861a 100644
--- a/utils/io/coercecolumn.go
+++ b/utils/io/coercecolumn.go
@@ -74,7 +74,7 @@ func (cs *ColumnSeries) CoerceColumnType(columnName string, elementType EnumElem
 	case reflect.Uint64:
 		newCol := make([]uint64, columnValues.Len())
 		for i := 0; i < columnValues.Len(); i++ {
-			newCol[i] = uint64(toUint(columnValues.Index(i)))
+			newCol[i] = toUint(columnValues.Index(i))
 		}
 		cs.columns[columnName] = newCol
 	case reflect.Float32:
diff --git a/utils/io/columnseries.go b/utils/io/columnseries.go
index ed8f0ec9..ee7fa5a4 100644
--- a/utils/io/columnseries.go
+++ b/utils/io/columnseries.go
@@ -229,7 +229,6 @@ func (cs *ColumnSeries) GetEpoch() []int64 {
 		return nil
 	}
 	return col.([]int64)
-
 }
 
 func (cs *ColumnSeries) ToRowSeries(itemKey TimeBucketKey, alignData bool) (rs *RowSeries, err error) {
diff --git a/utils/io/datashape.go b/utils/io/datashape.go
index cc38f3ca..b8664b56 100644
--- a/utils/io/datashape.go
+++ b/utils/io/datashape.go
@@ -89,7 +89,7 @@ func (ds *DataShape) toBytes() ([]byte, error) {
 func dsFromBytes(buf []byte) (ds DataShape, cursor int) {
 	cursor = 0
 	dsNameLen := int(ToUint8(buf[cursor : cursor+1]))
-	cursor ++
+	cursor++
 	dsName := ToString(buf[cursor : cursor+dsNameLen])
 	cursor += dsNameLen
 	dsType := EnumElementType(buf[cursor])
@@ -110,7 +110,7 @@ func DSVFromBytes(buf []byte) (dataShape []DataShape, byteLength int) {
 	ret := make([]DataShape, dsLen)
 
 	// deserializes each data shape
-	cursor ++
+	cursor++
 	for i := 0; i < dsLen; i++ {
 		ds, l := dsFromBytes(buf[cursor:])
 		ret[i] = ds
diff --git a/utils/io/numpy.go b/utils/io/numpy.go
index a49f6160..acc93b54 100644
--- a/utils/io/numpy.go
+++ b/utils/io/numpy.go
@@ -89,7 +89,6 @@ func (nds *NumpyDataset) buildDataShapes() ([]DataShape, error) {
 			return nil, fmt.Errorf("unsupported type string %s", typeStr)
 		}
 		etypes = append(etypes, typ)
-
 	}
 	return NewDataShapeVector(nds.ColumnNames, etypes), nil
 }
diff --git a/utils/io/rowseries.go b/utils/io/rowseries.go
index 39145694..de8ea6ae 100644
--- a/utils/io/rowseries.go
+++ b/utils/io/rowseries.go
@@ -224,7 +224,7 @@ func (rs *RowSeries) GetTime() ([]time.Time, error) {
 }
 
 func (rs *RowSeries) GetEpoch() (col []int64) {
-	return getInt64Column(0, int(rs.GetRowLen()), rs.GetNumRows(), rs.GetData())
+	return getInt64Column(0, rs.GetRowLen(), rs.GetNumRows(), rs.GetData())
 }
 
 func (rs *RowSeries) ToColumnSeries() (key TimeBucketKey, cs *ColumnSeries) {
diff --git a/utils/test/setup.go b/utils/test/setup.go
index fe8ba33f..9dba5da5 100644
--- a/utils/test/setup.go
+++ b/utils/test/setup.go
@@ -160,7 +160,7 @@ func WriteDummyData(f *os.File, year, tf string, makeGap, isStock bool) (int, er
 			candlesCurrency = append(candlesCurrency, ohlc{ind, o, h, l, c})
 		}
 		//		fmt.Printf(":%d:",ind)
-		index ++
+		index++
 	}
 
 	var (