From Junior to Senior Developer: Skills That Actually Matter

The gap between junior and senior developers isn't about knowing more frameworks or languages — it's about how you approach problems, communicate solutions, and make decisions under uncertainty.

Think in Systems, Not Features

Junior developers implement features. Senior developers design systems. Before writing code, ask: How does this feature affect the rest of the application? What happens when it fails? How will this scale? What will we need to change in 6 months? This systems thinking prevents architectural debt that's expensive to fix later.

Master the Art of Code Review

Great code reviews aren't about catching bugs — linters and tests handle that. Focus on architecture, maintainability, and knowledge sharing. Ask "Why did you choose this approach?" rather than "This is wrong." Suggest alternatives with explanations. A good reviewer makes the whole team better, not just the code.

Write Code for Humans First

Code is read 10x more than it's written. Choose clear variable names over clever ones. Write functions that do one thing with descriptive names. Add comments for why, not what — the code explains what it does, but context about business decisions or non-obvious tradeoffs belongs in comments.

Debug Methodically

Senior developers don't randomly change things until the bug goes away. They form hypotheses, test them systematically, and understand the root cause before writing a fix. Learn to read stack traces, use step debuggers (Xdebug for PHP), and write regression tests that prove the bug existed and is now fixed.

Communicate Technical Decisions

The most valued senior developers explain complex technical concepts to non-technical stakeholders. Practice writing clear technical proposals, documenting architecture decisions (ADRs), and presenting tradeoffs in terms of business impact. "This refactor will take 2 weeks but reduce our bug rate by 40%" is better than "We need to refactor because the code is messy."

Growth happens outside your comfort zone. Take on projects that scare you, mentor someone junior, contribute to open source, and read code from developers better than you. The senior title follows naturally.