Compatibility: Valkey/Redis OSS protocol (open-source, same drivers and tools)
Serverless: No (provisioned node clusters with sharding)
Scale to zero: No
VPC required: Yes
Multi-region: Multi-Region active-active (eventually consistent cross-region, strongly consistent within region)
Free Tier: None (covered by $100-200 new-account credits)
Min cost: ~$75/month (db.t4g.small, single shard + 1 replica)
Time to first query: 5-10 min (VPC + cluster creation)
Key features: Microsecond reads / single-digit ms writes, Multi-AZ durable transactional log, vector search (HNSW, single-digit ms at 99%+ recall), JSON document support, data tiering (memory + SSD for nearly 5x capacity at 60% lower cost), 160M+ requests/sec per cluster, 100+ TB storage, sharding, ACLs
Limitations: No scale to zero, VPC required, provisioned capacity only, in-memory cost scales with data size, Multi-Region excludes data tiering and vector search
Best for: Workloads requiring multi-region active-active writes (strongly consistent within region, eventually consistent cross-region) — the capability that distinguishes MemoryDB from ElastiCache
Not for: Single-region workloads (ElastiCache offers the same durability, vector search, and microsecond latency at lower cost with a Serverless option), large analytical datasets, relational data with JOINs, workloads needing scale-to-zero cost efficiency