Purpose

The indexer keeps the backend in sync with onchain state so the relayer can resolve accounts quickly.

Why it exists

Without the indexer, every authenticated request would require the relayer to scan the onchain AccountRegistry to find which MemWalAccount holds a given delegate key. This involves fetching the registry object, iterating through its dynamic fields, and checking each account, an expensive chain of RPC calls.

The indexer eliminates this by listening to Sui events and syncing account data into PostgreSQL. The relayer can then resolve delegate key ownership with a single database lookup.

How it works

The indexer is a standalone Rust service (services/indexer) that:

1. Connects to the same PostgreSQL database as the relayer
2. Polls Sui blockchain events using suix_queryEvents
3. Filters for AccountCreated events from the Walrus Memory package
4. Inserts account_id → owner mappings into the accounts table
5. Stores its event cursor in indexer_state so it can resume after restarts

Auth resolution flow

When the relayer receives a request, it resolves the delegate key's account using this priority:

1. PostgreSQL cache (delegate_key_cache), fastest, populated lazily by the relayer itself
2. Indexed accounts (accounts), populated by the indexer, enables account discovery without chain scans
3. Onchain registry scan, fallback, scans AccountRegistry dynamic fields through RPC
4. Header hint (x-account-id), client-provided hint, useful during first-time setup
5. Config fallback (MEMWAL_ACCOUNT_ID), server-level default

After successful resolution through any strategy, the mapping is cached in delegate_key_cache for future requests.

Configuration

The indexer reads these environment variables:

Variable	Required	Default	Description
DATABASE_URL	Yes		PostgreSQL connection string
MEMWAL_PACKAGE_ID	Yes		Walrus Memory contract package ID to filter events
SUI_RPC_URL	No	Mainnet fullnode	Sui RPC endpoint
POLL_INTERVAL_SECS	No	5	Seconds between event poll cycles

Running

$ cd services/indexer
$ cargo run

The indexer is recommended for production but optional for development, the relayer can fall back to onchain resolution without it.