deserve what you wanthttps://jieun.dev/https://jieun.dev/en/blog/no-traffic-startup-to-global-scale-an-inversion-checklist/https://jieun.dev/en/blog/no-traffic-startup-to-global-scale-an-inversion-checklist/How do you get from a small no-traffic company to a global-scale service? Don't ask "how do I get there" — ask "how do I guarantee I stay stuck." Six traps, each as problem → fix.Tue, 07 Jul 2026 00:00:00 GMThttps://jieun.dev/en/blog/designing-a-generation-pipeline-a-4-axis-content-model-queue-based-scheduling-3-layer-attribution/https://jieun.dev/en/blog/designing-a-generation-pipeline-a-4-axis-content-model-queue-based-scheduling-3-layer-attribution/Part 2 of an engineering log on building a Threads marketing agent: a content model decomposed into four axes, an idempotent publish worker, and 3-layer attribution where 90% of clicks were bots.Mon, 29 Jun 2026 00:00:00 GMThttps://jieun.dev/en/blog/designing-a-crawler-that-beats-three-tiers-of-anti-bot-from-tls-fingerprints-to-cdp-detection/https://jieun.dev/en/blog/designing-a-crawler-that-beats-three-tiers-of-anti-bot-from-tls-fingerprints-to-cdp-detection/Part 1 of an engineering log on building a Threads marketing agent: the bottleneck was never LLM generation — it was crawling. Tiering the strategy by which signal the anti-bot actually inspects.Mon, 29 Jun 2026 00:00:00 GMThttps://jieun.dev/en/blog/scaling-qps-10x-in-production-3-strategies-that-actually-move-the-needle/https://jieun.dev/en/blog/scaling-qps-10x-in-production-3-strategies-that-actually-move-the-needle/"Make it faster" sounds vague. It isn't — it comes down to the same three moves: caching, database optimization, and pulling non-essential work out of the request.Fri, 29 May 2026 00:00:00 GMThttps://jieun.dev/en/blog/there-was-a-deadlock-hiding-in-ai-generated-code-how-we-replaced-unreadcount-with-lastreadat/https://jieun.dev/en/blog/there-was-a-deadlock-hiding-in-ai-generated-code-how-we-replaced-unreadcount-with-lastreadat/42.8% HTTP error rate, 9 minutes into a load test, at 12% of the target TPS. The culprit was a single updateMany line written during AI-assisted coding.Mon, 11 May 2026 00:00:00 GMThttps://jieun.dev/en/blog/building-a-reusable-load-test-environment-for-a-messenger-service-make-based-iac-observability-and-auth-seeding/https://jieun.dev/en/blog/building-a-reusable-load-test-environment-for-a-messenger-service-make-based-iac-observability-and-auth-seeding/How many TPS can a messenger's send API survive, and where exactly does it break? A 7-node mirror of production, rebuilt on demand from a single Makefile target.Mon, 11 May 2026 00:00:00 GMThttps://jieun.dev/en/blog/why-you-should-never-use-keydb-as-a-pub-sub-broker-for-centrifugo/https://jieun.dev/en/blog/why-you-should-never-use-keydb-as-a-pub-sub-broker-for-centrifugo/KeyDB's active-replica mode looked perfect for a symmetric dual-stack chat at 100K WebSocket connections. Then I found five years of hang and deadlock issues, most still open.Sun, 29 Mar 2026 00:00:00 GMThttps://jieun.dev/en/blog/building-a-crash-resilient-end-to-end-meeting-recording-pipeline-in-the-browser/https://jieun.dev/en/blog/building-a-crash-resilient-end-to-end-meeting-recording-pipeline-in-the-browser/A one-hour browser recording could push the JS heap past 300 MB, and a tab crash meant losing everything. Rebuilding it as a six-stage pipeline with five-minute savepoints.Thu, 26 Mar 2026 00:00:00 GMT