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 ...
Role of IP Addresses in System Design and Architecture When people start learning system design , IP addresses often feel confusing or too technical. But in reality, IP addresses are one of the simplest and most important ideas behind how systems work. If you understand IP addresses properly, many things suddenly become clear: How websites work Why databases are not exposed to the internet How systems scale safely Let’s break this down slowly and simply . What Is an IP Address? An IP address is a number that identifies a device on a network . Every device connected to a network needs one: Mobile phone Laptop Server Database Think of an IP address like a home address . If someone wants to send you a letter, they need your home address If one computer wants to send data to another, it needs the IP address Example: 192.168.1.10 This number tells the network: “Send data to this exact device.” Without IP addresses, computers would not kno...
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