We do need to maintain code quality and standards. There are a few guidelines for collaboration:
If you are working on an issue that touches on areas outside of your expertise, be sure to mention someone in the other group(s) as you soon as you start working on it. This allows others to give you early feedback, which should save you time in the long run.
Security: If a frontend developer needs to touch controller code, a backend developer/miniboss/endboss should do a thorough review.
Big features/moonshots: If we do something ambitious where there are no previous examples and requires a high degree of complexity in both frontend and backend, form a team upfront that has UX designers, frontend, and backend engineers.
Final review: A final review of a merge request should be made by an endboss. If it is mainly frontend code it should be reviewed by a frontend endboss, and it it is mainly backend code it should be reviewed by a backend endboss.