Chat in a secondhand marketplace app has to work for reading and writing on the subway. Design the local database schema and the sync flow so that messages sent offline reach the server later and order, duplicates, and read state stay straight.
The local database is the source of truth, and a message carries a localId, a serverId, a status (pending, sent, failed), and the server seq. Sending inserts locally and an outbox queue transmits, the server takes the localId as an idempotency key, ordering comes from the server seq, and on reconnect you take only the delta after lastSeq.
iOS system designShort answerBasics
Design a simple notes app. Walk me through the architecture, how you store the data, and…
#offline-first #sync #swiftdata
iOS system designShort answerBasics
How is an "offline-first" app architecture different from the usual "network first, fall…
#offline-first #outbox #sync
iOS system designShort answerAdvanced
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#chat #outbox #idempotency
PersistenceShort answerExpert
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#sync #swiftdata