[Elaticsearch] concurrent writing to multiple indexes
After #10156 (closed), we should consider engineering a way for us to keep multiple elasticsearch indexes up to date at the same time.
When we're creating a new index, in order to allow the old index to still work, we need to read from the old index and write to the new index - but this means the old index is going to get outdated since no writes will go to it. If that's acceptable then there's no further action needed, but if not then we need to write our own layer between ES and us that knows how to write to multiple indexes (and it also won't be as simple as that, because an update operation wouldn't work on the new index if it doesn't yet have the underlying document)
Elasticsearch does not have a native way to write to two indexes, so it would fall on us to write one.