At high scale, you want to perhaps try your query a few more times, backing off exponentially, maybe even round-robining (or more complicated load balancing) among different targets. Throwing up your hands and 5xx-ing a request that easily is not something you can afford at high scales of traffic where small outages happen _all the time_.
so basically you mean that this only applies to like 0.001% of all websites/apps.
thus it's stupid to do it. I mean even than you would have an error that you need to bubble up or circuit break it somwhere but probably not at this layer.
also KISS and MVP, never ever overcomplicate something when you do not know anything yet, so most people don't need to built for scale at day 1 and it also is stupid to do it.