Stop Paying a Streaming Bus to Carry Bytes That Live for Ninety Seconds

Samar Prakash Posted on May 30 • Originally published at Medium Stop Paying a Streaming Bus to Carry Bytes That Live for Ninety Seconds # architecture # devops # java # aws How a shared filesystem became the cheapest, fastest outbox I've ever built — and why FSx for OpenZFS is the version of that idea that finally scales I was staring at an AWS bill last quarter where a single Kinesis Data Streams line item was costing more than the entire S3 footprint sitting behind it. The events on that stream had a useful lifetime of about ninety seconds. They were written by one service, read by another, processed, and dropped. We were paying full streaming-bus price for bytes that barely outlived a TCP timeout. That bill is what got me thinking about transitional data as a category that deserves its own architecture, and about why every "use the right tool" instinct I had — Kinesis, Kafka, MSK — was the wrong tool for this particular shape of work. The right tool, it turns out, is a filesystem. Specifically, AWS FSx for OpenZFS, used as an outbox between producers and consumers, with only a tiny pointer message traveling through whatever messaging bus you already have. This article is the case for that pattern. It's also the design, the failure modes, the code, the cost math, and the honest list of when not to do it. I'll walk you through the architecture from first principles, show you the safe-write protocol that makes it correct under crashes and concurrent retries, compare the cost against Kinesis, MSK and EFS at a realistic petabyte-class workload, and explain why the recent addition of FSx Intelligent-Tiering changes the cost story in a way that makes the pattern attractive even for teams that don't ingest petabytes. If you've ever felt the queasy sensation of paying twice for the same bytes — once to land on a stream, again to land in storage — this is for you. What "transitional data" actually means Most data falls into one of two cleanly shaped buckets. Durable d