> ## Documentation Index > Fetch the complete documentation index at: https://docs.trdrs.co/llms.txt > Use this file to discover all available pages before exploring further. # Backfill history > Windows, countBack paging, the two signals that tell you to stop scrolling — and the handoff to the live stream. [Get price history](/api-reference/market-data/get-price-history) has two modes, and picking the wrong one is the usual cause of a chart that scrolls forever. A plain window answers "what happened between these two times". `countBack` answers "give me the N bars before this point" — the scroll-back page — and it outranks `from` when both are sent. With no range at all, the route answers the most recent 500 bars or so. It is the fastest way to get something on screen. ```bash theme={null} curl "$TRDRS_API_BASE_URL/api/market/history?instrument=ESU6&tf=5m" \ -H "Authorization: Bearer $TRDRS_TENANT_KEY" ``` Bars come back as `{ t, o, h, l, c, v }` with `t` in epoch seconds. `from` and `to` are epoch seconds, inclusive at both ends. ```bash theme={null} curl "$TRDRS_API_BASE_URL/api/market/history?instrument=ESU6&tf=5m&from=1787500000&to=1787586400" \ -H "Authorization: Bearer $TRDRS_TENANT_KEY" ``` The window's width is capped in bars by `limits.maxBars` from [the limits route](/api-reference/market-data/get-market-data-limits) — the same number that caps `countBack`. Ask for a wider span at a finer timeframe and you are asking for more bars than the route will serve. `countBack` asks for the last N bars at or before `to`. This is the call a chart makes when the user drags the view left. ```bash theme={null} curl "$TRDRS_API_BASE_URL/api/market/history?instrument=ESU6&tf=5m&to=1787500000&countBack=500" \ -H "Authorization: Bearer $TRDRS_TENANT_KEY" ``` Set `to` to the timestamp of the oldest bar you currently hold and ask again for the next page. `countBack` outranks `from`, so send `to` and `countBack` and leave `from` out of it. Once the backfill is on screen, [open a bar stream](/api-reference/market-data/stream-live-bars) for the same instrument and timeframe. On every connect the stream replays a full `snapshot` and then applies live `bar` events, so the two views converge without you reconciling them. ```bash theme={null} curl -N "$TRDRS_API_BASE_URL/api/market/stream?instrument=ESU6&tf=5m" \ -H "Authorization: Bearer $TRDRS_TENANT_KEY" ``` ## The two signals that end a scroll-back Both are present only when they are true, so treat an absent field as false. | Signal | What it means | What to do | | -------------- | ------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------ | | `noData: true` | The `countBack` answer came back empty. | Stop scrolling back. There is nothing older to fetch at this timeframe. | | `stale: true` | Every bar served predates the asked `countBack` window — a closed market. | Render it as history, not as now. It is what stops a consumer mistaking Friday's bars for a live Saturday session. | A chart that ignores `noData` keeps asking for pages that will never exist. A chart that ignores `stale` shows a weekend as if the market were open. ## Spread expressions The `instrument` may be an arithmetic expression over instruments rather than a single symbol — `ES-NQ`, `1/ESU6`, `(ES+NQ)/2`. | | | | --------------------- | --------------------------------------------------------------- | | Operators | `+ - * / ^`, parentheses, and numeric literals | | Legs | up to four instruments | | Where it is evaluated | server-side, over the bucket intersection of the legs | | Which buckets exist | only those every leg printed — a spread bar exists nowhere else | | Volume | `0` on every spread bar | An exact catalog match always wins over arithmetic: the slash pair `BTC/USD` is the symbol, never a division. The same expression [resolves under symbol details](/api-reference/market-data/get-symbol-details) as type `spread`, with no tick and no quote surface, and it [streams](/api-reference/market-data/stream-live-bars) like any other instrument — though any single leg's refusal refuses the whole spread. ## When history refuses | Status | What it means | | ------ | -------------------------------------------------------------------------------------------------------- | | `400` | A malformed timeframe token or parameter. The route fails closed rather than guessing at what you meant. | | `429` | Rate limited. The `Retry-After` header carries the wait. | | `503` | No feed serves this instrument. | On futures the `503` body carries a typed code, and the three are different problems: | Code | What happened | What to do | | -------------------------- | ----------------------------------------------------------------------------------- | ------------------------------------------------ | | `feed_requires_connection` | Futures data streams from your own connected Rithmic account, and there is not one. | Connect an account. | | `feed_capacity` | The per-user session ceiling. | Retry shortly. | | `feed_displaced` | Another application took over this login's market-data session. | It is a conflict at the venue, not a fault here. | Anything else is `market_data_unavailable`. ## The pattern, in one line Fetch the limits once, resolve the symbol once, backfill a window, then stream — and page back with `countBack` until `noData` says stop. Everything else is presentation. ## Where to go deeper * [Find symbols](/guides/find-symbols) — the limits, the catalog, and the tick and format a bar needs to render. * [Stream live data](/guides/stream-live-data) — the snapshot-then-events contract that heals its own reconnects. * [Streaming](/partner-platform/overview/streaming) — the reconnect contract in full. * [Bring data via your venue](/guides/venue-data) — why a trader's own venue login is what serves these bars. * [Rate limits](/partner-platform/overview/rate-limits) — what the `429` is counting.