I have been developing a lot of Moodle tasks as following:

- Clearly define modular structure model to support micro-services for large scale Moodle websites.

- Moodle as the backend for React/Angular frontend.

- Customizing course view with Moodle course formats.

- Creating, developing, integrating and maintaining a variety of plugins such as activities, resources, local plugins, blocks...

- Improving the performance of existing processes because of data growing day by day. This can be achieved by effectively/efficiently using Moodle cache mechanism.

- Creating numerous cron-tasks to transfer student marks/grades to external webservices and to normalize data for complicated reports.

- Clearly defining access-right for users by combination of role, capability, permission  and context. This is sometimes tricky even for developers.

- Overwriting Moodle core functions without changing Moodle core code.

- Building a variety of reports about marks/grades, attendance, student submissions...

- Synchronizing data between Moodle and external systems.

- Enabling Moodle to communicate with outside end via a set of functions from Moodle built-in web-services.

- Building GDPR compliance to plugins. This is very important to work with users in Europe.

- Building Unit tests/Automation test with Behat, Selenium.

I'm the head of Moodle solutions at Harvey Nash Group with 10+ years of experience in Moodle. I have been working with various roles such as full-stack dev, technical lead, project manager...

I support many universities in England and Europe to successfully apply Moodle into their business.

Here are some Moodle websites that I was working with UOLW (University of London Worldwide), MMU (Manchester Metropolitan University), King's College, OU (Open University)...:

https://soas-vle2-uat.bloom.ulcc.ac.uk/
https://laws.elearning.london.ac.uk/
https://moodle.bbk.ac.uk/
https://github.com/ULCC/open-mod_coursework (this is contributed to Moodle community).