--- title: "Fernando Castellanos (@masitecno) | Hashnode" description: "Practical notes from a backend developer debugging real-world systems. Read the latest articles by Fernando Castellanos on Hashnode." url: "https://hashnode.com/@masitecno" --- @masitecno # Fernando Castellanos @masitecno · Joined June 2026 Practical notes from a backend developer debugging real-world systems. ### [From Smoke Tests to Production Truth: Lessons from Load Testing Five APIs with Locust](https://backend-debugging.hashnode.dev/from-smoke-tests-to-production-truth-lessons-from-load-testing-five-apis-with-locust?utm_source=hashnode&utm_medium=feed) Load testing five backend APIs with Locust: clean scaling, saturation, empty-payload traps, and why zero failures can still be a performance failure. 17 min read · [backend-debugging.hashnode.dev](https://backend-debugging.hashnode.dev/from-smoke-tests-to-production-truth-lessons-from-load-testing-five-apis-with-locust?utm_source=hashnode&utm_medium=feed) [Jul 27](https://hashnode.com/posts/from-smoke-tests-to-production-truth-lessons-from-load-testing-five-apis-with-locust/6a6790a35fcb8a8e87729de8) ### [The Bug Wasn't in Our Code](https://backend-debugging.hashnode.dev/the-bug-wasn-t-in-our-code?utm_source=hashnode&utm_medium=feed) A production debugging story about temporal coincidence, evidence, and why the most recent change is the easiest suspect to convict by mistake. 8 min read · [backend-debugging.hashnode.dev](https://backend-debugging.hashnode.dev/the-bug-wasn-t-in-our-code?utm_source=hashnode&utm_medium=feed) [Jun 30](https://hashnode.com/posts/the-bug-wasn-t-in-our-code/6a4438dec4917bda90cbc71e) ### [How I Use AI Assistants for Debugging Without Trusting Them Blindly](https://backend-debugging.hashnode.dev/how-i-use-ai-assistants-for-debugging-without-trusting-them-blindly?utm_source=hashnode&utm_medium=feed) A practical workflow for backend developers who want speed without losing judgment. 10 min read · [backend-debugging.hashnode.dev](https://backend-debugging.hashnode.dev/how-i-use-ai-assistants-for-debugging-without-trusting-them-blindly?utm_source=hashnode&utm_medium=feed) [Jun 25](https://hashnode.com/posts/how-i-use-ai-assistants-for-debugging-without-trusting-them-blindly/6a3ca7a88713ea09760d1d6f)