Most of the programmers in their 30s have enough experience to finish a full stack product or at least entire feature set on their own.<p>But many company's interview process includes competitive problem solving, within space and time complexity, memory requirements etc. the platforms to practice such problems are in worst state, most of them are paid and rest of them target jobs and interviews instead of improving logic. at least that's my experience.<p>What the platforms you are aware of to improve logic solving, free and open platforms preferred.
If you want to get good at something, practice that thing. It sounds like you're asking how to get good at coding interviews. So practice coding interview questions, not logic problems or competitive programming. LeetCode is probably the best known coding interview practice platform right now, and it has hundreds of free problems. In the LeetCode discussions, you can find people reporting on their interview experience, and companies often ask identical problems to the ones on the site. It's exactly optimized for what it says it's for.<p>You could get better at logical problem solving by practicing on Khan Academy or Brilliant or Art of Problem Solving. If that's what you want, then do those things. But it's not an efficient way to get better at interview questions.