# MongoDB Search synonym map update propagation and validation > Source-anchored research for MongoDB Search synonym map update propagation and validation. Run status: COMPLETED. Parent: [MongoDB Atlas Search](https://llms-explorer.com/tree/mongodb-atlas-search/) · 2 facets · 9 facts · page: https://llms-explorer.com/tree/mongodb-search-synonym-map-update-propagation-and-validation/ ## Problems, failure modes and limitations - The Atlas Admin API exposes synonymMappingStatus with FAILED, BUILDING, and READY values, plus synonymMappingStatusDetail for each search host, including an optional error message and a mapping queryable flag. These fields appear only when synonyms are defined. (low confidence) — [source](https://www.mongodb.com/docs/api/doc/atlas-admin-api-v2/operation/operation-updategroupclustersearchindexbyname) - In a June 2023 first-person failure report, array and empty-string validation missed the synonym entry ["∞"] under lucene.standard. The reporter identified that document as the cause of index build failure; the thread does not establish a universal prohibition on symbol characters. (low confidence) — [source](https://www.mongodb.com/community/forums/t/search-index-creation-fails-when-synonyms-list-are-provided/232592) - A May 2023 forum report alleged that multiword synonym entries were invalid, but the responder said the supplied examples should be supported and requested the index definition, query, and exact error. The thread does not establish that spaces alone invalidate synonym entries. (low confidence) — [source](https://www.mongodb.com/community/forums/t/entering-an-open-compound-word-in-synonyms-in-synonym-collection-renders-the-document-invalid/228014) - A first-person Reddit failure report contains an unknown synonym mapping name error: the query uses searchSynonyms while the index names its mapping synonyms and its source collection searchSynonyms. This is evidence of a name mismatch in the posted configuration, not proof that a cluster upgrade broke update propagation. (low confidence) — [source](https://www.reddit.com/r/mongodb/comments/s0kzjs) ## Facts and statements - MongoDB Search watches changes to the synonym source collection and automatically updates its internal synonym map; editing those documents does not require reindexing. (low confidence) — [source](https://www.mongodb.com/docs/search/indexes/synonyms.md) - Synonym source-document changes appear in query results eventually. Update time increases with the size of the synonym source collection; the reference gives no fixed propagation deadline. (low confidence) — [source](https://www.mongodb.com/docs/search/indexes/synonyms.md) - MongoDB recommends batching inserts and updates to synonym source collections. Large synonym collections create larger in-memory mapping artifacts, even though mapping definitions require no additional disk space beyond the source collection. (low confidence) — [source](https://www.mongodb.com/docs/search/performance/index-performance.md) - Invalid documents in a referenced synonym source collection can prevent Search index creation. MongoDB recommends validating document format and expected behavior in a test environment before adding synonym documents in production. (low confidence) — [source](https://www.mongodb.com/docs/search/indexes/synonyms.md) - Atlas lists FTS_INDEXES_SYNONYM_MAPPING_INVALID as an alertable event named Synonym Mapping Invalid. (low confidence) — [source](https://www.mongodb.com/docs/atlas/reference/atlas-alert-event-types.md)