RDS, Aurora & DynamoDB
Relational vs NoSQL, replicas, caching.
AWS offers a database for every workload, and matching the data model to the right managed service is a core architecture skill. The big distinction is relational (RDS/Aurora) versus NoSQL (DynamoDB), with caching and analytics services alongside.
Relational: RDS and Aurora
Amazon RDS is a managed relational database (MySQL, PostgreSQL, SQL Server, Oracle, MariaDB) where AWS handles patching, backups, and replication so you run a database, not a server. Two features do the architecture heavy lifting: Multi-AZ deployment provides high availability via a synchronous standby in another AZ with automatic failover, and read replicas scale read-heavy workloads by offloading queries to asynchronous copies. Amazon Aurora is AWS’s MySQL/PostgreSQL-compatible engine with a distributed storage layer replicated across three AZs, delivering higher performance and faster failover than standard RDS. Reach for relational when you need joins, transactions, and a fixed schema.
# RELATIONAL (RDS / Aurora) NOSQL (DynamoDB)# joins, transactions, fixed schema key-value/document, massive scale# Multi-AZ → HA (standby + failover) managed, serverless, single-digit ms# read replicas → scale READS auto-scales throughput, no servers# vertical scaling for writes partition-key design drives performance## cache hot reads → ElastiCache (Redis/Memcached) or DynamoDB DAX# analytics/warehouse → Amazon Redshift
NoSQL, caching, and analytics
Amazon DynamoDB is a fully-managed, serverless NoSQL key-value and document database delivering single-digit-millisecond latency at any scale, with no servers to manage and automatic scaling — ideal for high-throughput applications, session stores, and workloads that outgrow a single relational instance. Get the partition-key design right and it scales seamlessly. To reduce read load and latency, Amazon ElastiCache (Redis or Memcached) puts a managed in-memory cache in front of a database, and DynamoDB has DAX for the same. For analytics over large datasets, Amazon Redshift is the managed data warehouse. The architect’s job is choosing the purpose-built service for the workload rather than forcing everything into one database.