The answer to this question is always use Redis or memcached. Nothing you whip up on your own is ever going to be a good as a well tested cache implementation t

The answer to this question is always use Redis or memcached. Nothing you whip up on your own is ever going to be a good as a well tested cache implementation that has seen every edge case. This is the difference between a mid-level and a senior engineer during an interview. The latter will explain to you the pitfalls of what you are asking for before even considering writing a line of code.