A few years ago I wrote down advice for fixing slow SQL queries.
Today, that kind of writing should probably be turned into a skill.
Here is the original guide:
https://github.com/ekeric13/sql-query-optimization-guide
And here is its conversion into a skill:
https://github.com/ekeric13/sql-query-optimization-skill
If you have a query that is performing poorly, try it out! It is postgres focused.
FYI - I would keep skills like this off by default. It is domain specific. And most engineers aren't spending all day doing SQL query optimization work, so there is no reason to pollute the context window until it is actually needed.
If you have old writings about best practices, it is definitely worth your time to turn them into a skill. With the use of an LLM it will take about 10 min, even if you have never made a skill before.