Interviewing Backend Tech Leads

I am a Senior Software Engineer at a Fintech startup based out of Bangalore, with 6 years of experience in Backend Engineering. I wanted to write this blog primarily for myself, so that in case I interview for a lead position, I can keep these learnings at the back of my mind.

Recently, I was tasked with taking the first round of interviews for a backend tech lead position. The first round involved a technical discussion, where the candidate was given a design or coding problem (e.g., designing an in-memory database or status tracker). This was to gauge the candidate’s ability to interpret the problem, communicate effectively, and approach the solution. We allowed candidates to use any internet resources, including their preferred LLMs, since coding without StackOverflow or ChatGPT is rare nowadays.

Here are some red flags I identified in candidates I rejected:

• Not understanding the problem and jumping straight to solving it
• Not asking questions and assuming things
• Not communicating the reasons behind their actions, especially for major design choices
• Not writing modularized code
• Failing to apply design patterns after verifying code functionality; I believe good code should start well-organized from the beginning
• Not knowing basic design patterns like Repository, Strategy, Facade, Factory, and Builder
• Not understanding where SOLID principles can be applied, including dependency inversion
• Lacking basic database knowledge, such as ACID, transactions, isolation levels, and index structures, which I find crucial in a backend lead with 10-12 years of experience
• Assuming too much during design conversations, which is a personal pet peeve