import type { MigrationTracker } from '../types';
/**
 * Periodically refreshes the migration lock so that migrations longer than
 * the lock TTL don't have their lock taken by another worker.
 *
 * Returns a stop function. Call it from the same `finally` that releases
 * the lock to make sure the interval doesn't leak.
 *
 * The heartbeat fires every `ttlSeconds / 3` seconds. Errors from the
 * underlying refresh are logged and swallowed: if the lock is genuinely
 * lost, the next tracker mutation will fail its ConditionCheck and the
 * runner will surface a clear `TransactionCanceledException` to the user.
 */
export declare function startLockHeartbeat(tracker: MigrationTracker, ttlSeconds: number): () => void;
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