Tip 6 Swiss Cheese Model | Better Programmer

Tip 6 How to be a better junior programmer Today's tip is about the Swiss Cheese Model and why multiple layers of defence matter in code. In the 1990s, a psychologist named James Reason studied major accidents—plane crashes, nuclear incidents, medical errors—and discovered something fascinating. He found that disasters rarely happen because of a single failure. Instead, they occur when multiple small failures align, like holes in slices of Swiss cheese stacking up to create a straight path through. Each slice of cheese represents a defensive layer—a safety check, a validation, a backup system. Individually, each layer has imperfections or holes if you like. When you stack multiple layers, the holes rarely line up, so things work. A problem only occurs when the holes line up, and it slip through every single layer for disaster to strike. The same principle applies to software. Junior developers often rely on a single layer as a point of defence in code. Let’s take input validation as an example. You might write some code in the user interface that disables the “Save” button if the user doesn’t enter a value for all required fields. That’s great, but what if a malicious user bypasses your user interface and invokes your API directly? If you don’t validate on the server, then it’s possible for a dodgy submit to corrupt your database. The Solution: Build multiple layers of defence into your code. Validate user input on the frontend for user experience, but also validate on the backend for security. Don’t just rely on one layer. Each layer doesn't have to be perfect—it just needs to catch what the previous layer missed. When you stack these defensive layers, your code becomes resilient. A single failure becomes an inconvenience rather than a catastrophe. Just like that, you're a better developer. I'm posting every weekday. See you tomorrow! User Mastery - Helping product teams engage with their users https://usermastery.com #programming #juniordev #coding #developer #tech