> ## Documentation Index
> Fetch the complete documentation index at: https://docs.moralis.com/llms.txt
> Use this file to discover all available pages before exploring further.

# History & Backfill: How Far Back Do You Need to Index?

> Some Data Feeds answers need full history to be correct (balances, holders); others only need as much history as you want to show (swaps, logs, prices). Here's how to tell, and how to scope your backfill.

When you move an endpoint onto Data Feeds, one early decision shapes your setup cost: **how far back does the
sink need to index?** Get it right and you avoid both wasted backfill and, more importantly, silently wrong
results. The answer depends on whether the endpoint returns **current state** or an **event list**.

## The rule of thumb

> **Current-state answers need full history. Event-list answers need only as much history as you want to show.**

### Current state → needs full history

Balances, holders, approvals, native balances, total supply, token metadata, these describe **what is true
right now**, and "right now" is the cumulative result of **every past event**. You can't know a wallet's current
balance without its most recent transfer, and that transfer could have happened at any point since the token
launched.

Data Feeds make this efficient, each transfer carries the **absolute balance after it** (`*PostBalance`), so a
recipe just keeps the *latest* observation per holder rather than replaying every delta. But "latest" still
means you must have **seen** each holder's most recent transfer. Start indexing too late and you simply **miss**
every holder whose last activity predates your start, an incomplete, quietly wrong result.

So for correctness, backfill from the beginning of the relevant history:

* **By a single token** (e.g. all holders of token X) → from **that token's first block** (its deployment).
  You don't need chain genesis, just everything since the token existed. Much cheaper.
* **By a wallet across all tokens** (e.g. a wallet's full balance set) → effectively **full history**, because
  the wallet may still hold something it last touched years ago.

### Event list → your choice

Swaps, transfers, raw logs, price history, NFT trades, a wallet's activity feed, these are **append-only
streams of past events**. Each event is independent, so there's no cumulative state to reconstruct. Backfill is
purely a **product decision**: how much history do you want to display or analyze?

* Only need new activity from now on? Run **realtime** with no backfill.
* Want the last 90 days, or since a token launched, or everything? Backfill to that point.
* Either way the data is correct, you're just choosing the window.

## Quick reference

| If the endpoint returns…                                     | Type          | Backfill you need                                       |
| ------------------------------------------------------------ | ------------- | ------------------------------------------------------- |
| Token holders / balances **by token**                        | current state | from the **token's first block**                        |
| Wallet token balances / net worth **by wallet**              | current state | **full history**                                        |
| Native balance, approvals, total supply                      | current state | full history (or token's first block, if token-scoped)  |
| Token metadata (name/symbol/decimals)                        | current state | back to the **token's deployment** (or read from chain) |
| Swaps / transfers / logs / prices / trades / wallet activity | event list    | **your choice** (realtime, or any window)               |

## How to set it

Recipes run in three modes, **historical** (backfill a window), **realtime** (live tail), or **hybrid**
(backfill then hand off to live). For current-state answers, use historical or hybrid with the start block set
to the beginning of the relevant history (`MORALIS_HISTORICAL_FROM_BLOCK`); for event lists, pick whatever
window your product needs, or realtime-only.

<Note>
  **Scope your backfill to save time.** Indexing a single token's holders from its deployment block is far
  cheaper than indexing the whole chain from genesis. Only the broad, by-wallet/chain-wide current-state cases
  truly need full history.
</Note>

Each migration guide states the specific answer for its endpoint up front, so you can size the backfill before
you start.