Part 8 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 . We built an engine with no ignition Here's where we actually stood after seven parts of this series. We had a fully working AuthService — register, login, refresh, the works. We had a security layer sitting on top of it, filtering every request, deciding who's allowed where. We had entities, repositories, DTOs, a whole exception-handling backbone. And none of it had a URL. Not one line of that code could be reached from outside the JVM. No curl command, no Postman request, nothing. It's a strange feeling to have written that much working logic and still not be able to actually call any of it. So that's what this part is about — wiring up the front door. The controller, and why it's boring on purpose Here's the register endpoint, in full: @PostMapping ( "/registe...
Java Streams Explained Clearly (Java 8–21): Intermediate, Terminal, Lazy Execution, Stateless vs Stateful, and takeWhile() / dropWhile() Java Streams are one of the most important features introduced in Java 8 , and they are now used heavily in real-world backend projects and Java interviews . In this article, you will learn Java Streams from the ground up , including: What Java Streams are and why they exist Intermediate vs Terminal operations Why streams are lazy Stateless vs Stateful operations (very important) takeWhile() and dropWhile() explained in detail (Java 9+) Performance and parallel streams Common mistakes and interview questions This guide is written in simple language , with clear examples , and is suitable for beginners, working professionals, and interview preparation . What Are Java Streams and Why Were They Introduced? Before Java 8, most data processing in Java was done using lo...
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