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Side-by-side decisions on cost, scale, consistency, and when each option wins. Leave with a choice, not just a definition.
PostgreSQL vs MySQL
Two mature open-source relational databases. Postgres is richer (types, constraints, query power, extensibility); MySQL is lighter, ubiquitous, and very fast for simple read-heavy web workloads. Both are single-primary and need sharding at scale.
See the decisionPostgreSQL vs DynamoDB
A general-purpose relational DB vs a managed key-value/document store. Postgres gives full SQL and query flexibility you operate yourself; DynamoDB gives horizontal scale and zero ops for key-based access patterns, at the cost of query flexibility.
See the decisionRedis vs Memcached
Two in-memory caches. Redis offers rich data types, persistence, replication, and pub/sub (single-threaded per core); Memcached is simpler, multithreaded, strings-only, and intentionally ephemeral. Both are excellent; the choice is about features vs simplicity.
See the decisionKafka vs SQS
A durable, replayable distributed log vs a managed task queue. Kafka is for event streaming with multiple consumers and replay; SQS is for decoupling producers and workers with at-least-once delivery and no ops. Different tools for different patterns.
See the decisionREST vs gRPC
HTTP/JSON resources vs typed, binary RPC over HTTP/2. REST is universal, cacheable, and browser-friendly; gRPC is efficient, typed, and streaming-capable for internal service-to-service calls. Not mutually exclusive — use a gateway to expose gRPC as REST.
See the decision