The euw table is essentially a caching layer. Now that we have code (with foreign API requests) to recompute the values in it, we should replace it with a real caching layer.

We already have the counts+timestamps for each section in each wiki's cache, so if there's an API for building a key for a different wiki (we already assume a shared cache, because we use global cache keys) then we could grab each wiki's count and timestamp directly from its cache. Then we'd only need to cache/store lists of wikis.