[BACK] Add cache'ing for most endpoints

[ArielMAJ]

Type of feature

🍕 Feature

Current behavior

Currently, if the server is on free tier, the CPU is so low that it takes a few seconds to load data. Considering data won't change very often, it would make sense to cache some of the information for faster loading/response for at least a few seconds or minutes (and invalidate cache on changes).

Suggested solution

Add in-memory caching to most routes.

Additional context

No response

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