Ask HN: How do you become good at competitive programming

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.

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.

What the platforms you are aware of to improve logic solving, free and open platforms preferred.