At my corporate job, I work in Java, python in cloud providers like GCP and Azure. We use a lot of open source stuff like Apache Commons, beam, spark etc. Wondering how to start contributing to open source as beginner as I don't have knowledge about the internals of any of them.
If you are already using open source tools within your organization, a good way to start getting involved is to report bugs to those upstream projects when they happen.
If you want to contribute more directly I'd recommend with simple improvements to the documentation of a project that you use. While you might not be interested in documentation work in the long term it is a good way of becoming familiar with the project's specific process of merging new contributions. Once the first contribution has been made to a project it should be somewhat easier to navigate their trackers to understand what sort of programming roles are available.
Check out http://up-for-grabs.net for a consistent source of open source projects that could use some help. There are also specific tags that indicate first-timer friendly contributions.
If you want to contribute more directly I'd recommend with simple improvements to the documentation of a project that you use. While you might not be interested in documentation work in the long term it is a good way of becoming familiar with the project's specific process of merging new contributions. Once the first contribution has been made to a project it should be somewhat easier to navigate their trackers to understand what sort of programming roles are available.