Part 9 of 10 of Building Instagram's Authentication Backend . If you're just joining, the repo is here and you can catch the earlier parts on the YouTube playlist . Eight parts of code, zero runs By the end of part 8, every layer of this backend existed: DTOs, exceptions, entities, repositories, five services, a security filter chain and a controller. And I had never started the application. Not once. Everything so far was code I'd reasoned through and believed would work. This part is where that belief gets tested. We containerize the app, put Postgres, Redis and a fake mail server next to it, and bring all four up with one command. It did not work the first time, so this post is the real debugging session, with each bug, its symptom and its fix. If you're containerizing your own Spring Boot app, there's a good chance you'll hit at least one of these. In this post: A multi-stage Dockerfile for Spring Boot, line by line A docker-compose.yml ...
Backend Deep-Dive · Opinion + Code · ~14 min read · Updated for 2026 Python vs Java for Backend in the AI Era Every few months someone asks me — on YouTube, on Topmate, in a mock interview — "Prashant, should I learn Python or Java for backend?" And every time, I give the same unsatisfying answer: it depends on what you're building. I know that sounds like a cop-out. But I've spent years writing Java in production — Spring Boot services handling real traffic, real transactions, real on-call pages at 2 AM — and I also teach Python, write automation scripts in it, and have built small backends with FastAPI. I'm not neutral because I lack opinions. I'm neutral because I've seen both languages do things the other genuinely cannot do well. This post is my honest, experience-based take. I'll show you the same endpoint built in both Spring Boot and FastAPI, talk about where each one starts to hurt in production, and give you the decisio...
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