Amazon MemoryDB
Durable in-memory database
An in-memory database compatible with Valkey and Redis OSS, but durable: every write is stored in a Multi-AZ transaction log, so it can serve as a primary database, not just a cache.
- Cost$$$ High
- Difficulty●●●●●
- Costs money when idle?Yes
- Managed by AWS
- In examsSAA
Think of it asLike a wall board that's very fast to read, but every time you write on it a copy also goes into the ledger.
When to use it
✓ Use it when
You need in-memory speed and Redis data structures for primary data, with no tolerance for data loss.
✗ Avoid it when
You only need a temporary, cheaper cache → ElastiCache; large-scale serverless key-value → DynamoDB.
Common uses
- Sessions and shopping carts that must be durable
- Real-time leaderboards and counters
- Microservices needing a low-latency database
What does it cost?
- Pricing model: Charged hourly per node, plus GB of data written to the transaction log and snapshots beyond the free allowance.
Related services
SAA-C03 study guide
MemoryDB is covered in these study modules: