Why Cassandra handles high-frequency writes better than PostgreSQL

Cassandra can absorb thousands of independent device writes per second by spreading them across servers and batching disk I/O on each one. Each write is appended to a commit log and held in an in-memory memtable, which is later flushed in sorted order to an SSTable, following a log-structured merge tree design. PostgreSQL also uses a write-ahead log, but it must update heap pages and indexes as each row arrives, so a single primary can become a bottleneck under heavy insert rates. Cassandra shifts some work into background compaction, which must keep pace to sustain throughput, while partitioning lets multiple servers process writes in parallel. The article notes that PostgreSQL can still handle high insert rates within its primary's capacity, and that the outcome depends on hardware, schema, durability settings, and how evenly writes are distributed.