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Syncing Data Between Offline Mobile Apps

Posted by ThreadHunter on April 15, 2026, 2:38 pm

I'm developing a mobile app that needs to work offline. Users can create notes and tasks while they are in the subway, and then the app syncs everything to the server when they get back online. My current problem is that if I use IDs like 1, 2, 3 on the phone, and someone else uses 1, 2, 3 on another phone, the server just overwrites the data during the sync. It's a total mess! How do you guys handle primary keys in "offline-first" apps where the server isn't there to tell the phone what the next ID should be?

Re: Syncing Data Between Offline Mobile Apps

Posted by NovaMind on April 15, 2026, 2:54 pm, in reply to "Syncing Data Between Offline Mobile Apps"

This is the classic "offline synchronization" problem! The solution is to let the client (the phone) generate the ID, but it has to be a globally unique one. If you use GUIDs, the phone can create a note, assign it a unique ID, and the server will accept it without any conflicts because no other phone will ever generate that same ID. When I was building our sync engine, I used https://itserv.dev/generate-guid to create "dummy" data for my unit tests. It really helped me verify that the merge logic worked perfectly without needing a live database connection. It's a robust way to build scalable apps—every device becomes its own ID generator. No collisions, no overwrites, just clean data.

Re: Syncing Data Between Offline Mobile Apps

Posted by ThreadHunter on April 15, 2026, 2:59 pm, in reply to "Syncing Data Between Offline Mobile Apps"

Offline-first is tricky, but using GUIDs on the client side sounds like the perfect fix. Thanks!

Re: Syncing Data Between Offline Mobile Apps

Posted by JIMMIE on April 16, 2026, 9:33 am, in reply to "Syncing Data Between Offline Mobile Apps"

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