Incremental Sync
A sync that transfers only records added, changed, or deleted since the last successful run instead of copying everything again.
See it
What it is
An incremental sync copies only what changed after the previous successful run. The first run builds a full local copy; later runs ask for updates and deletions after a timestamp, change token, or cursor. Google Calendar's Events API, for example, returns a sync token that can be used to request the next set of changes.
Reach for it when a full export is slow, expensive, or rate limited. Process every page, apply each change idempotently, and save the next cursor only when the whole batch is durable. Treat deletions as data too; otherwise removed source records live forever in the mirror.
Incremental feeds are not eternal truth. Tokens expire, filters change, and a bug can advance the checkpoint past unprocessed data. Google Calendar returns HTTP 410 when a sync token is no longer valid, which means the client must clear its local state and perform a full sync. Keep that reset path tested and run periodic reconciliation to catch silent drift.
Ask AI for it
Build an incremental Google Calendar Events sync. Perform the initial events.list crawl through every nextPageToken, store the returned nextSyncToken only after all pages commit, and use that syncToken on later runs. Apply changed events idempotently by event ID, treat cancelled events as deletions, and never advance the token after a partial failure. When Google Calendar returns HTTP 410 for an expired token, clear the local calendar mirror and run a fresh full sync. Add tests for pagination, deletion, crash recovery, and token expiry.