The services at a glance
| Service | Type | Use when… |
|---|---|---|
| RDS | Managed relational | You want managed MySQL/PostgreSQL/Oracle/SQL Server/MariaDB. |
| Aurora | Cloud-native relational | MySQL/PostgreSQL compatibility with higher performance and auto-scaling storage. |
| DynamoDB | NoSQL key-value/document | Serverless, single-digit-millisecond scale; unpredictable/huge throughput. |
| ElastiCache | In-memory cache | Sub-ms caching/sessions with Redis or Memcached. |
| Redshift | Data warehouse (OLAP) | Analytics over large datasets with columnar storage. |
| DocumentDB | Document (MongoDB-compatible) | JSON document workloads with MongoDB APIs. |
| Neptune | Graph | Highly connected data — social, fraud, recommendations. |
OLTP vs OLAP — the key split
The deciding question
OLTP (many small transactions → RDS/Aurora/DynamoDB) vs OLAP (analytical queries over big data → Redshift). Getting this right answers most "which database" exam questions.
Exam traps
- Redshift for transactions. It's a warehouse (OLAP), not for high-volume OLTP.
- DynamoDB for complex joins/relations. It's key-value; relational needs RDS/Aurora.
- ElastiCache as a primary store. It's a cache layer, not durable primary storage.
Test yourself
4 quick questions — tap an answer to check it instantly. Nothing is sent anywhere.
1. Which service is a managed data warehouse (OLAP)?
Answer: C. Redshift is the columnar OLAP data warehouse.
2. Which is a NoSQL key-value/document database?
Answer: B. DynamoDB is the managed NoSQL key-value/document service.
3. ElastiCache is used for…
Answer: B. ElastiCache (Redis/Memcached) is an in-memory cache, not a primary store.
4. OLTP (many small transactions) is best served by…
Answer: B. OLTP workloads use RDS/Aurora or DynamoDB; Redshift is OLAP.
Sources
- Amazon Web Services — AWS Databases.
- AWS official documentation and the AWS Certified Solutions Architect exam guide.
Reference summary only. "AWS" is a trademark of Amazon. Confirm current details in the official AWS documentation.