sync-validate

Run this review against src/index.ts to check each sync against a fourteen-point checklist. It reports findings grouped by severity: critical issues that break the sync, structural bi-modal problems, and warnings that cause subtle data quality bugs.

Infinite loops happen when nextState never advances or hasMore never becomes false. Skipped records usually come from missing overlap windows during backfill-to-delta transitions or a cursor that advances past records not yet indexed by an eventually consistent API.

Use incremental mode when the source API supports change tracking such as updated_at filters or event feeds, since replace mode re-fetches everything each cycle. Replace mode is appropriate when the API has no delete signal or change tracking capability.

Check whether the source API exposes a delete signal such as an audit log, archived filter, or event stream. If it does, emit delete markers with the record key; if the signal lives on a separate endpoint, alternate streams at cycle boundaries using the flip-flop pattern.

Timestamp cursors fail when multiple records share the same updated_at value, which is common with batch imports or low-resolution timestamps. The fix is the keyset pattern using a compound cursor of timestamp plus id with a tie-breaking query.