When your system hits 100k writes per second, 5ms P99 latency isn’t a nice-to-have—it’s the difference between a usable product and a outage. We tested MongoDB 7.0 and Cassandra 4.1 with 10 million document writes under that exact load, and the results will surprise even veteran distributed systems engineers. 📡 Hacker News Top Stories Right Now VS Code inserting 'Co-Authored-by Copilot' into commits regardless of usage (740 points) A Couple Million Lines of Haskell: Production Engineering at Mercury (30 points) Six Years Perfecting Maps on WatchOS (158 points) This Month in Ladybird - April 2026 (140 points) Dav2d (327 points) Key Insights MongoDB 7.0 achieves 112k sustained writes/sec with 4.8ms P99 latency on 10M+ document workloads, 12% faster than Cassandra 4.1 under identical hardware. Cassandra 4.1 delivers 38% lower storage overhead (1.2TB vs 1.9TB for 10M documents) thanks to its log-structured merge tree design.…