Personal writing by Pankaj Chauhan on software engineering, system design, distributed systems, databases, backend engineering, and AI.https://pankajchouhan.dev/en-us© 2026 Pankaj Chauhanhttps://pankajchouhan.dev/blog/designing-a-url-shortener-everything-i-learned-after-reading-a-dozen-articles-and-failing-this-question-once/https://pankajchouhan.dev/blog/designing-a-url-shortener-everything-i-learned-after-reading-a-dozen-articles-and-failing-this-question-once/My personal notes on the classic 'design a URL shortener' interview question — the parts every article agrees on, the parts they don't, and the follow-up questions that actually got asked to me.Tue, 25 Aug 2026 00:00:00 GMTSystem DesignPankaj Chauhanhttps://pankajchouhan.dev/blog/designing-a-rate-limiter/https://pankajchouhan.dev/blog/designing-a-rate-limiter/A complete rate limiter design: algorithms, Redis implementations, distributed coordination, and the interview trade-offs that matter.Thu, 20 Aug 2026 00:00:00 GMTSystem DesignRate LimitingRedisSystem DesignInterviewsPankaj Chauhanhttps://pankajchouhan.dev/blog/how-redis-distributed-locks-work/https://pankajchouhan.dev/blog/how-redis-distributed-locks-work/A practical explanation of Redis distributed locking, Redlock, fencing tokens, and the failure modes that show up in production.Wed, 12 Aug 2026 00:00:00 GMTSystem DesignRedisDistributed SystemsSystem DesignPankaj Chauhanhttps://pankajchouhan.dev/blog/kafka-partitions-explained/https://pankajchouhan.dev/blog/kafka-partitions-explained/What a Kafka partition really is, how keys map to ordering, and why consumer groups live or die by partition count.Tue, 28 Jul 2026 00:00:00 GMTDistributed SystemsKafkaDistributed SystemsMessagingPankaj Chauhanhttps://pankajchouhan.dev/blog/understanding-database-sharding/https://pankajchouhan.dev/blog/understanding-database-sharding/How sharding actually works: partition keys, scatter-gather queries, resharding, and the operational costs that diagrams leave out.Mon, 15 Jun 2026 00:00:00 GMTDatabasesDatabasesShardingSystem DesignPankaj Chauhanhttps://pankajchouhan.dev/blog/how-a-url-shortener-works/https://pankajchouhan.dev/blog/how-a-url-shortener-works/System design for a URL shortener: encoding, storage, redirects, caching, and the abuse problems that appear at real traffic.Sat, 02 May 2026 00:00:00 GMTSystem DesignSystem DesignHTTPDatabasesPankaj Chauhan