https://ashwingopalsamy.in/library Books, watching, notes, and links en https://ashwingopalsamy.in/library/notes/designing-rate-limiters-for-payment-systems https://ashwingopalsamy.in/library/notes/designing-rate-limiters-for-payment-systems Tue, 07 Apr 2026 00:00:00 GMT notes Rate limiting in payment systems is different from rate limiting in a typical web API. A false positive -- rejecting a legitimate authorization -- is a failed transaction. A customer's card gets… https://ashwingopalsamy.in/library/notes/understanding-iso8583-bitmaps https://ashwingopalsamy.in/library/notes/understanding-iso8583-bitmaps Wed, 01 Apr 2026 00:00:00 GMT notes Every ISO 8583 message begins with a Message Type Indicator (MTI), followed by one or two bitmaps that declare which data elements are present in the message. What is a Bitmap? A bitmap is a binary… https://ashwingopalsamy.in/library/notes/go-error-wrapping https://ashwingopalsamy.in/library/notes/go-error-wrapping Sat, 28 Mar 2026 00:00:00 GMT notes The pattern is the standard way to add context to errors in Go. But there are nuances worth knowing. Always wrap with context that answers "what were you trying to do?" not "what went wrong?" The… https://ashwingopalsamy.in/library/notes/litellm-supply-chain-attack https://ashwingopalsamy.in/library/notes/litellm-supply-chain-attack Wed, 25 Mar 2026 00:00:00 GMT notes On March 24, 2026, Callum McMahon at FutureSearch was testing a Cursor MCP plugin that pulled in litellm as a transitive dependency. Shortly after, his machine became unresponsive. He traced it to a… https://ashwingopalsamy.in/library/notes/consistent-hashing-distributed-caches https://ashwingopalsamy.in/library/notes/consistent-hashing-distributed-caches Sun, 15 Mar 2026 00:00:00 GMT notes When you distribute data across multiple cache nodes, the naive approach is modular hashing: . This works until you add or remove a node. The Problem with Modular Hashing If you have 4 nodes and add… https://ashwingopalsamy.in/library/notes/slog-structured-logging https://ashwingopalsamy.in/library/notes/slog-structured-logging Tue, 10 Mar 2026 00:00:00 GMT notes Go 1.21 introduced in the standard library. For new projects, I now default to slog over zerolog. 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Read from stdin, normalize the input, increment the value for the keys in a . The output looked sorted. Alphabetically sorted. I ran it again. Same order.… https://ashwingopalsamy.in/library https://ashwingopalsamy.in/library Thu, 20 Nov 2025 00:00:00 GMT books https://ashwingopalsamy.in/library/notes/go-floating-point-tolerance-testing https://ashwingopalsamy.in/library/notes/go-floating-point-tolerance-testing Sun, 17 Aug 2025 00:00:00 GMT notes Last Tuesday, I was knee-deep in a financial calculation service when my tests started failing. You know that sinking feeling when doesn't equal ? That was my afternoon. This got me thinking about… https://ashwingopalsamy.in/library https://ashwingopalsamy.in/library Fri, 15 Aug 2025 00:00:00 GMT books https://ashwingopalsamy.in/library/notes/runes-bytes-and-graphemes-in-go https://ashwingopalsamy.in/library/notes/runes-bytes-and-graphemes-in-go Sat, 09 Aug 2025 00:00:00 GMT notes I once ran into this problem while handling names in Tamil and emoji in a Go web app: a string that looked short wasn't, and reversing it produced gibberish. 1. Bytes Go represents strings as… https://ashwingopalsamy.in/library/notes/go-was-never-bad https://ashwingopalsamy.in/library/notes/go-was-never-bad Sat, 21 Jun 2025 00:00:00 GMT notes Every time I see that GitHub repo go-is-not-good making the rounds again, I laugh. It's always shared by people who mistake language cleverness for engineering. Let me say this clearly: Go is not for… https://ashwingopalsamy.in/library https://ashwingopalsamy.in/library Sun, 15 Jun 2025 00:00:00 GMT watch https://ashwingopalsamy.in/library/notes/go-goroutine-stack-growth https://ashwingopalsamy.in/library/notes/go-goroutine-stack-growth Sun, 08 Jun 2025 00:00:00 GMT notes If you ask any mid-senior Go dev what makes goroutines lightweight you'll get the reply: They start with 2 KB of stack instead of 1 MB like OS threads. They're not wrong. But they're not thinking… https://ashwingopalsamy.in/library/notes/go-scheduler-infinite-loops https://ashwingopalsamy.in/library/notes/go-scheduler-infinite-loops Sat, 24 May 2025 00:00:00 GMT notes I've been reviewing performance-critical code, and I keep coming back to this pattern: versus The runtime implications are fascinating. 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With this post, I'll walk you through what is,… https://ashwingopalsamy.in/library/notes/go-program-entry-point https://ashwingopalsamy.in/library/notes/go-program-entry-point Fri, 13 Dec 2024 00:00:00 GMT notes When we first start with Go, the function seems almost too simple. But before even begins, the Go runtime orchestrates careful initialization of all imported packages, runs their functions and… https://ashwingopalsamy.in/library https://ashwingopalsamy.in/library Sun, 01 Dec 2024 00:00:00 GMT books https://ashwingopalsamy.in/library/notes/go-pointers-and-memory-management https://ashwingopalsamy.in/library/notes/go-pointers-and-memory-management Sun, 17 Nov 2024 00:00:00 GMT notes When I first started learning Go, I was intrigued by its approach to memory management. Go handles memory in a way that's both efficient and safe, but it can be a bit of a black box if you don't peek… https://ashwingopalsamy.in/library https://ashwingopalsamy.in/library Fri, 15 Nov 2024 00:00:00 GMT watch https://ashwingopalsamy.in/library/notes/git-practices-for-production-codebases https://ashwingopalsamy.in/library/notes/git-practices-for-production-codebases Thu, 14 Nov 2024 00:00:00 GMT notes Git is the backbone of every software project. Working in FinTech systems, I've learned that Git isn't just a tool -- it's a shared language and a safety net. In FinTech and regulated environments,… https://ashwingopalsamy.in/library/notes/go-constants-beyond-basics https://ashwingopalsamy.in/library/notes/go-constants-beyond-basics Wed, 13 Nov 2024 00:00:00 GMT notes When I first got into Go, I thought constants were simple and limited -- just fixed values, nothing fancy. But as I delved deeper, I found they're quite versatile. 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