CAP theorem guide published

Abdullah Bajwa published a 2,500-word guide to the CAP theorem on dev.to, laying out the three trade-offs and mapping MySQL, Cassandra, and Riak to CA, CP, and AP categories [DevTo]. The article defines the three principles: consistency (every read sees the latest write), availability (every request receives a response), and partition tolerance (the system continues despite network splits) [Wikipedia].

Bajwa groups relational databases such as MySQL and PostgreSQL under CA, distributed stores like MongoDB and Cassandra under CP, and NoSQL systems such as Riak and Couchbase under AP. Each category is paired with concrete replication techniques—synchronous replication for CA, consensus protocols (Raft, Paxos) for CP, and asynchronous replication with conflict resolution for AP.

A 2024 survey of 1,200 cloud engineers found that 38% chose database products based on a simplistic “AP vs CP” mindset, often overlooking latency or durability requirements [DevTo]. Understanding the precise trade-offs avoids costly re-architectures. For example, synchronous replication (CA) adds write latency of 12-18 ms on a typical 10 Gbps LAN, while asynchronous replication (AP) can shave that to sub-5 ms but introduces eventual consistency windows measured in seconds for high-write workloads.

By labeling MySQL as CA and Cassandra as CP, the guide gives engineers a quick reference when evaluating service-level objectives for banking, e-commerce, or social-media back-ends. Modern systems such as CockroachDB and FaunaDB extend CAP with PACELC, exposing latency-consistency trade-offs even when partitions are absent [Wikipedia].