https://sameeralam3127.github.io/devops-case-studies/ Practical DevOps, SRE, Cloud and Platform Engineering case studies covering architecture, troubleshooting, automation, reliability, security and production operations. en https://sameeralam3127.github.io/devops-case-studies/04-kubernetes/crashloopbackoff-after-release/ https://sameeralam3127.github.io/devops-case-studies/04-kubernetes/crashloopbackoff-after-release/ A payments API enters CrashLoopBackOff fifteen minutes after a routine deploy. Separating a bad image from a bad config from a bad dependency, under a 15-minute stabilisation budget. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/04-kubernetes/oomkilled-under-load/ https://sameeralam3127.github.io/devops-case-studies/04-kubernetes/oomkilled-under-load/ A JVM service is killed by the kernel every few hours under peak traffic while its own heap metrics look healthy. Reading cgroup accounting, off-heap memory, and why raising the limit is usually the wrong fix. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/10-security/python-before-your-code-runs/ https://sameeralam3127.github.io/devops-case-studies/10-security/python-before-your-code-runs/ The interpreter, installer, test runner and import system can all execute code before your entry point does. What that means for supply-chain security and CI safety. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/interviewer-checklist/ https://sameeralam3127.github.io/devops-case-studies/system-design/interviewer-checklist/ Scoring a system design round consistently — requirements, estimation, architecture, trade-offs, communication. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/prompt-001-url-shortener/ https://sameeralam3127.github.io/devops-case-studies/system-design/prompt-001-url-shortener/ A timed prompt for designing a URL shortener, with the clarifications a strong candidate asks for. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/prompt-002-notification-service/ https://sameeralam3127.github.io/devops-case-studies/system-design/prompt-002-notification-service/ A timed prompt for designing a multi-channel notification service. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/prompt-003-chat-system/ https://sameeralam3127.github.io/devops-case-studies/system-design/prompt-003-chat-system/ A timed prompt for designing a real-time chat system. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/prompt-004-news-feed/ https://sameeralam3127.github.io/devops-case-studies/system-design/prompt-004-news-feed/ A timed prompt for designing a news feed, including the push-vs-pull fan-out decision. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/session-template/ https://sameeralam3127.github.io/devops-case-studies/system-design/session-template/ A structure for recording one mock system design round: what was asked, what was covered, and where the time went. Sun, 06 Sep 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/001-url-shortener/ https://sameeralam3127.github.io/devops-case-studies/system-design/001-url-shortener/ Designing a read-heavy URL shortener end to end — Base62 key space sizing, distributed ID generation, the 301-vs-302 decision that cannot be undone, four-tier caching, hot-link handling, and abuse control. Wed, 26 Aug 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/002-rate-limiter/ https://sameeralam3127.github.io/devops-case-studies/system-design/002-rate-limiter/ Designing a distributed rate limiter end to end — the five algorithms and when each is right, atomic token buckets in Redis, the two-tier local/central hybrid, hot-key sharding, per-route fail-open policy, and multi-region limit slicing. Wed, 26 Aug 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/005-notification-service/ https://sameeralam3127.github.io/devops-case-studies/system-design/005-notification-service/ Designing a multi-channel notification system end to end — accept-then-deliver queues, the eligibility pipeline that decides whether to send at all, template rendering, provider quotas and failover, retries without duplicates, bounce and suppression handling, and digesting. Mon, 10 Aug 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/004-chat-system/ https://sameeralam3127.github.io/devops-case-studies/system-design/004-chat-system/ Designing a real-time messaging system end to end — persistent connections and session routing, per-conversation ordering, at-least-once delivery with client dedupe, offline push, multi-device sync, presence, and where end-to-end encryption changes the architecture. Sun, 09 Aug 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/system-design/003-pastebin/ https://sameeralam3127.github.io/devops-case-studies/system-design/003-pastebin/ Designing a text-sharing service end to end — key generation, blob vs metadata storage, expiry and burn-after-read semantics, CDN-backed read path, and the optimizations that keep a read-heavy system cheap. Wed, 05 Aug 2026 00:00:00 GMT https://sameeralam3127.github.io/devops-case-studies/notes/markdown-reference/ https://sameeralam3127.github.io/devops-case-studies/notes/markdown-reference/ Everything the sd365 renderer supports — admonitions, emoji shortcodes, tags, diagrams, tables, and code blocks — with the source for each. Wed, 05 Aug 2026 00:00:00 GMT