What Should I Know as a Mid-Level Java Developer?

Be sure to know your Java collections and performance complexities. Writing code is a must, but when it comes to designing a REST API, focus on CRUD operations and understand additional functionalities that fit in with REST design principles. It's also essential to grasp concepts like backward and forward compatibility. And just a tip—avoiding writing Spring controllers during REST API design discussions can be beneficial; consider how those decisions shape application architecture.

As someone who does a lot of hiring, I look for problem-solving skills and a bit of enthusiasm. Whether you have 3 years or 30, your ability to tackle challenges is key. I might give you a scenario like testing three services and see how deep you can go. I’ll ask about basic data structures too, but I won't drill you on complex topics unless it’s crucial for the role. Show that you're excited about the position and go the extra mile if you do a take-home assignment—explain your choices clearly, even if something doesn't work out.

It varies from place to place, but generally, I'd expect a mid-level developer to ask as many questions as they get asked. You should be able to take most standard tickets and implement them without much guidance. For bigger or more complex tasks, you might find it challenging to come up with a solid solution or discuss the pros and cons of various options, but you should be able to hold your own in those conversations.

Oh, and as a side note, you shouldn’t box yourself in by calling yourself just a 'Java developer.' Java is just a programming language—if you can't adapt to others, that could be a red flag for hiring!