Pub/sub 1:1 (16B) improved from 0.18x to 0.50x, fan-out from 0.18x to 0.44x,
and JetStream durable fetch from 0.13x to 0.64x vs Go. Key changes: replace
.ToArray() copy in SendMessage with pooled buffer handoff, batch multiple small
writes into single WriteAsync via 64KB coalesce buffer in write loop, and remove
profiling Stopwatch instrumentation from ProcessMessage/StreamManager hot paths.
Add detailed analysis of the 1,200x JetStream file publish gap identifying
the bottleneck in the outbound write path (not FileStore). Add tests.md
tracking skipped/failing test status across Core and JetStream suites.
Implement Go-parity background flush loop (coalesce 16KB/8ms) in MsgBlock/FileStore,
replace O(n) GetStateAsync with incremental counters, skip PruneExpired/LoadAsync/
PrunePerSubject when not needed, and bypass RAFT for single-replica streams. Fix counter
tracking bugs in RemoveMsg/EraseMsg/TTL expiry and ObjectDisposedException races in
flush loop disposal. FileStore optimizations verified with 3112/3112 JetStream tests
passing; async publish benchmark remains at ~174 msg/s due to E2E protocol path bottleneck.
Side-by-side performance benchmarks using NATS.Client.Core against both
servers on ephemeral ports. Includes core pub/sub, request/reply latency,
and JetStream throughput tests with comparison output and
benchmarks_comparison.md results. Also fixes timestamp flakiness in
StoreInterfaceTests by using explicit timestamps.
