Offline-first is a product decision
Offline support is not a final polish task. It changes how users understand saved work, conflicts, timestamps, authentication and errors. The interface must make local and synchronized state understandable without forcing users to think like engineers.
Define the synchronization contract
For every important record, decide what can be created offline, what can be edited, how conflicts are resolved and what happens when the server rejects a change.
- Stable local identifiers
- Retry rules and backoff
- Conflict ownership
- Queued file uploads
- Deletion behavior
- Visible sync status
- Audit timestamps
Test the failure modes
Test airplane mode, slow networks, expired sessions, duplicated submissions, interrupted uploads, clock differences and an app being killed during synchronization. Happy-path testing on office Wi-Fi does not represent field conditions.
Measure reliability after launch
Track queue depth, retry frequency, sync duration, conflict rate and the age of unsynchronized records. These signals reveal operational problems before customer support tickets do.