Help Me Choose: OpenSearch, Redis, Kafka, or Postgres for Career Growth?

I’m at a point in my career where I need to specialize in one of the following technologies: OpenSearch, Redis, Kafka, or Postgres to become an SME [Subject Matter Expert], as asked by my manager. To make the best decision, I want to evaluate them based on salary potential, job opportunities, and long-term career growth. I want to focus on a technology that has strong demand now and promising future prospects. If you’re working with any of these, I’d love to hear your insights on which one offers the best career trajectory. Which one would you choose and why?