Follow GTFS-Realtime feed polling and freshness best practices
domain: gtfs.org · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Read the official best-practices guidance at gtfs.org/documentation/realtime/realtime-best-practices/ before building a polling loop
Poll each feed no less often than every 30 seconds, or faster if the underlying data changes more frequently (especially VehiclePositions)
Check FeedHeader.timestamp on every fetch and flag data older than the recommended freshness window (about 90 seconds for TripUpdates/VehiclePositions, about 10 minutes for Alerts)
Use HTTP conditional GET (If-Modified-Since) where the producer supports it to avoid re-transferring an unchanged feed
Treat feeds as stateless snapshots: if an entity present in one poll is absent in the next, treat it as no longer active rather than trying to diff/patch prior state
Known gotchas
Conditional GET support is inconsistent across producers; build a timestamp-based dedupe as a fallback rather than assuming If-Modified-Since always works
Intermittent malformed-protobuf responses are a real-world failure mode (best practice tolerates under 1% invalid responses) — wrap each fetch in its own error handling, not just the polling session as a whole
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