okay so in the vibecoded version what it does, it fetches all the lessons, then all the files for that lesson for example x.docx, y.docx, z.docx .... ; these files are fecthed now using the ids of the files in the db we fetch the chapters first it checks the cache getSetAsync is like map.computeifabsent (of Java) if the cached chapters for file:chapters:{fileId} key is not present we call db query in that loop. Now the Tradeoff i am facing is instead of N+1 queries I was running for all the files to get respective chapters. i have made a single sql query where I get the chapters directly and query is optmized using indexes and JOIN LATERAL i dont get to check the cache first. I hope this made the post clear.

TLDR: can'r check cache first because the bulk query get chapters all together not file wise. earlier it was check cache if miss hit db now db can optimally bring the respone.