The Hidden Cost of a Log Line : Sync/Async Flush and everything in Between

log.info("user logged in") looks free. It isn't. Behind that one line is a chain of decisions — buffer or not, flush or not, block or drop, same thread or another — and each one trades latency, throughput, and durability against the others. This post walks the whole chain, from the method call down to the bytes hitting the disk platter. If you've ever wondered why your p99 latency has a mysterious spike, why logs vanish after a crash, or what "async logging" actually buys you, this is for you