Never include comments in the function body (docstrings are okay).
Always avoid implicit boolean coercion e.g. use if len(data) == 0 instead of if not data, and if x is not None instead of if x.
Always spell out variable names fully. Avoid abbreviations e.g. use buttonElement instead of btn, categoryElements instead of catEls, subscription instead of sub.
Use StrEnum, CustomUuid, and NewType to represent distinct business objects that may have the same primitive type.
Use Pydantic BaseModel subclasses to represent domain models.
When developing a new user flow, always plan and write appropriate integration and E2E tests.
Avoid using defaults, whether in Python code or SQL, unless absolutely necessary.
When a repository method executes multiple queries, wrap them in self._executor.transactionally() to make them atomic.