https://blog.mohith16.com/ Technical deep dives on backend systems, infrastructure, and performance. en https://blog.mohith16.com/posts/the-sandbox-had-no-internet/ https://blog.mohith16.com/posts/the-sandbox-had-no-internet/ How OpenAI's evaluation agents turned a package mirror into a message board, escaped their sandbox, and compromised Hugging Face production systems. Thu, 27 Aug 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-10-invariants-i-didnt-hold/ https://blog.mohith16.com/posts/building-wal-10-invariants-i-didnt-hold/ An honest accounting of a write-ahead log: what it guarantees, where the documentation outran the code, and the pattern in every gap. Fri, 07 Aug 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-09-testing-crash-recovery/ https://blog.mohith16.com/posts/building-wal-09-testing-crash-recovery/ You can't unit test a power cut. What I built instead, and the gap I left in the middle of it. Tue, 04 Aug 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-08-checkpoints/ https://blog.mohith16.com/posts/building-wal-08-checkpoints/ A 2.55x speedup that was real, produced by a mechanism that doesn't exist, hiding a bug that resurrects deleted keys. Fri, 31 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-07-three-ways-to-recover/ https://blog.mohith16.com/posts/building-wal-07-three-ways-to-recover/ Recovery isn't about salvaging as much as possible. It's about knowing exactly where you stopped believing the file. Tue, 28 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-06-segments-and-rotation/ https://blog.mohith16.com/posts/building-wal-06-segments-and-rotation/ Splitting the log into files makes almost everything easier. The seam between writing and rotating is where a durability bug was hiding. Fri, 24 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-05-backpressure-and-cancellation/ https://blog.mohith16.com/posts/building-wal-05-backpressure-and-cancellation/ A bounded queue forces you to decide who waits. Cancellation forces you to decide what an error means. Tue, 21 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-04-group-commit/ https://blog.mohith16.com/posts/building-wal-04-group-commit/ Getting from 255 writes a second to nearly ten thousand, without weakening a single durability guarantee. Fri, 17 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-03-lsn-never-written-down/ https://blog.mohith16.com/posts/building-wal-03-lsn-never-written-down/ The LSN is the identity of every record in the log. It isn't stored on disk, and three problems follow from that. Tue, 14 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-02-twenty-two-bytes/ https://blog.mohith16.com/posts/building-wal-02-twenty-two-bytes/ A length prefix tells you where a record ends. A checksum tells you whether to believe the length prefix. Fri, 10 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-wal-01-what-a-wal-promises/ https://blog.mohith16.com/posts/building-wal-01-what-a-wal-promises/ The durability primitive underneath every database, and the one number that shapes every decision in it. Tue, 07 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-10-reliability-envelope/ https://blog.mohith16.com/posts/building-jobqueue-10-reliability-envelope/ An honest accounting of what this job queue guarantees, what it doesn't, and the config settings that do nothing at all. Fri, 03 Jul 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-09-tracing-async-boundary/ https://blog.mohith16.com/posts/building-jobqueue-09-tracing-async-boundary/ Parent and child is a claim about containment. Queued work isn't contained by anything, so it needs a different relationship. Tue, 30 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-08-load-test-that-failed/ https://blog.mohith16.com/posts/building-jobqueue-08-load-test-that-failed/ 173,000 requests with zero errors told me nothing useful. The test that broke its own thresholds told me everything. Fri, 26 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-07-crash-recovery/ https://blog.mohith16.com/posts/building-jobqueue-07-crash-recovery/ A status column records what a job was doing. It cannot record whether anyone is still doing it. Tue, 23 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-06-deadlines-and-blocking-work/ https://blog.mohith16.com/posts/building-jobqueue-06-deadlines-and-blocking-work/ Deadlines protect the worker, not the job. Once blocking code is involved, the difference stops being academic. Fri, 19 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-05-idempotency/ https://blog.mohith16.com/posts/building-jobqueue-05-idempotency/ Check-then-insert looks correct and isn't. The only reliable fix is to stop checking and let a constraint decide. Tue, 16 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-04-retries-backoff-jitter/ https://blog.mohith16.com/posts/building-jobqueue-04-retries-backoff-jitter/ Retrying is easy. Deciding when to retry, and making sure everyone doesn't decide the same thing, is the actual work. Fri, 12 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-03-priority-sorted-set/ https://blog.mohith16.com/posts/building-jobqueue-03-priority-sorted-set/ A single Redis sorted set gives strict priority and FIFO inside each tier. Then I checked the arithmetic. Tue, 09 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-02-two-stores-one-job/ https://blog.mohith16.com/posts/building-jobqueue-02-two-stores-one-job/ Splitting durable truth from fast dispatch buys a lot. It also creates a dual write I never made atomic. Fri, 05 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-jobqueue-01-why-not-celery/ https://blog.mohith16.com/posts/building-jobqueue-01-why-not-celery/ A job queue is a promise that work you accepted will eventually happen. Making that promise honestly is the hard part. Tue, 02 Jun 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-10-what-id-do-differently/ https://blog.mohith16.com/posts/building-canvas-10-what-id-do-differently/ Looking back at a collaborative canvas app, the decisions that held up, the ones that didn't, and what's still broken. Thu, 28 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-09-collaborative-undo/ https://blog.mohith16.com/posts/building-canvas-09-collaborative-undo/ Ctrl+Z is trivial in a single user app. Add one collaborator and the obvious implementation starts erasing other people's work. Sun, 24 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-08-offline-and-reconnect/ https://blog.mohith16.com/posts/building-canvas-08-offline-and-reconnect/ Rooms live in memory and get thrown away. The client is the persistence layer, which changes what reconnecting means. Wed, 20 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-07-backpressure/ https://blog.mohith16.com/posts/building-canvas-07-backpressure/ Every broadcast loop contains an assumption that send() works. Backpressure is what you build when it doesn't. Sun, 17 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-06-presence-and-cursors/ https://blog.mohith16.com/posts/building-canvas-06-presence-and-cursors/ Presence looks like the easiest feature in a collaborative app. It has the tightest constraints of anything in the system. Thu, 14 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-05-binary-protocol/ https://blog.mohith16.com/posts/building-canvas-05-binary-protocol/ What actually goes over the wire in a collaborative canvas, and why the ready made library didn't fit. Mon, 11 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-04-realtime-collaboration/ https://blog.mohith16.com/posts/building-canvas-04-realtime-collaboration/ Two people editing the same canvas is not a networking problem. It's an agreement problem. Fri, 08 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-03-freehand-drawing/ https://blog.mohith16.com/posts/building-canvas-03-freehand-drawing/ Freehand input looks simple, but the amount of data it generates can quickly overwhelm your rendering system. Tue, 05 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-02-rendering-engine/ https://blog.mohith16.com/posts/building-canvas-02-rendering-engine/ Rendering isn’t just about drawing shapes. It’s about controlling how much work happens per frame. Sun, 03 May 2026 00:00:00 GMT https://blog.mohith16.com/posts/building-canvas-01-about/ https://blog.mohith16.com/posts/building-canvas-01-about/ Performance issues don’t show up immediately, they build up quietly until your assumptions stop working. Thu, 30 Apr 2026 00:00:00 GMT