# Partition-Based Sync (Legacy) > Source-anchored research for Partition-Based Sync (Legacy). Run status: COMPLETED. Parent: [MongoDB Realm Mobile Sync](https://llms-explorer.com/tree/mongodb-realm-mobile-sync/) · 2 facets · 12 facts · page: https://llms-explorer.com/tree/partition-based-sync-legacy/ ## Comparisons and alternatives - User, team, channel, geographic-region, and time-bucket partitions were documented strategies; region and time ranges required discrete buckets rather than range matching. (low confidence) — [source](https://medium.com/realm/realm-provisioning-strategies-2431e02bb498) - MongoDB's Admin API notice, retrieved October 23, 2026, states that Atlas Device Sync reached end of life on September 30, 2025. Partition-Based Sync should therefore be described as a historical service capability rather than an available hosted-service recommendation. (low confidence) (verified as of 2026-10-23) — [source](https://www.mongodb.com/docs/api/doc/atlas-app-services-admin-api-v3) - A single partition-based Realm selected an exact partition value rather than a range, pattern, or union of several values. An application needing several partitions could open separate synced Realms. (medium confidence) — [source](https://medium.com/realm/realm-provisioning-strategies-2431e02bb498) - Range-like use cases required discrete partition buckets. Sharing overlapping data could require duplication in the backend; selecting multiple regions required multiple Realms rather than one range-based partition request. (low confidence) — [source](https://medium.com/realm/realm-provisioning-strategies-2431e02bb498) ## Facts and statements - Partition-Based Sync selected one partition field across synced collections; documents sharing its value belonged to the same partition, and a client opened a Realm for that value. (high confidence) — [source](https://www.mongodb.com/community/forums/t/mobile-bytes-5-understanding-partition-based-sync-and-flexible-sync/149265) - Choosing a partition value in the client did not itself grant access. Backend partition rules authorized access and could deny it, allow reads only, or allow reads and writes; the legacy permission boundary lacked per-document filtering within that partition. (high confidence) — [source](https://medium.com/realm/realm-provisioning-strategies-2431e02bb498) - Changing a document’s partition value was implemented as deleting it from one partition and inserting it into another. (low confidence) — [source](https://medium.com/realm/realm-provisioning-strategies-2431e02bb498) - The Realm Lua bootcamp's partition example warns that documents without its required partition field, or with a value different from the opened Realm's value, do not sync down to that device. (low confidence) — [source](https://github.com/realm/realm-lua-bootcamp) - In May 2024, a practitioner reported trouble moving a partition-based Realm into a Flexible Sync app. The Stack Overflow question names Duncan Groenewald; GitHub issue #6670 credits duncangroenewald and was opened the same day. Treat these as one apparent contributor report, not independent confirmations. (medium confidence) — [source](https://github.com/realm/realm-js/issues/6670) - Stack Harbor’s guide, labeled updated February 17, 2026, presents Device Sync as an operational product, conflicting with MongoDB’s notice that it reached EOL on September 30, 2025. (medium confidence) (verified as of 2026-02-17) — [source](https://stackharbor.com/en/knowledge-base/mongodb-atlas-sync-mobile/) - Common historical partition strategies used user IDs, teams or stores, channels, geographic regions, or time buckets. The strategy determined which data the device stored and which users shared that data. (low confidence) — [source](https://medium.com/realm/realm-provisioning-strategies-2431e02bb498) - A developer's May 17, 2024 firsthand report describes an existing partition-based synced Realm and a JavaScript workflow that read an existing local Realm file and wrote its data into a synced Realm. This is evidence of historical use, not a general guarantee for every SDK. (low confidence) — [source](https://stackoverflow.com/questions/78495130/how-can-i-load-a-mongodb-partition-based-synced-realm-to-flexible-sync-realm-usi)