Atlas Stream Processing cached lookup TTL and eviction
Parent: MongoDB Atlas Stream Processing · Published reference · snapshot 2026-10-29
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Source-anchored research for Atlas Stream Processing cached lookup TTL and eviction. Run status: COMPLETED.
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Structure and components
- The required ttl document contains integer size and unit: ms, second, minute, hour, or day. Entries are evicted when TTL elapses. (low confidence) (verified as of 2026-10-14) [source]
How it works
- MongoDB recommends caching static or slowly changing reference data; its tier guide recommends higher tiers when large reference sets need more cache RAM. (low confidence) (verified as of 2026-10-14) [source]
- Inference: TTL is not a guaranteed residence time, because memory-pressure eviction can remove cached results earlier. (low confidence) (verified as of 2026-10-14) [source]
Problems, failure modes and limitations
- At the memory limit, eviction frees space for new results. The syntax table describes older/expired results first, then random eviction if insufficient. (low confidence) (verified as of 2026-10-14) [source]
- maxMemUsageBytes defaults to 10% of workspace RAM and cannot exceed 12.5%, according to the syntax table. (low confidence) (verified as of 2026-10-14) [source]
Facts and statements
- $cachedLookup joins stream messages to an Atlas collection registered in the Connection Registry and caches query results. (low confidence) (verified as of 2026-10-14) [source]
- $cachedLookup does not support let or pipeline fields. (low confidence) (verified as of 2026-10-14) [source]
- The 19 August 2025 release added $cachedLookup; the 27 August release added lifetime cache hit/miss statistics under stats.operatorStats. (low confidence) [source]
Children
- No children recorded.