LevelDB is only used for indexes to look up series files by sets of dimensions, not for time-based lookups. We just need to find the right time series that are

LevelDB is only used for indexes to look up series files by sets of dimensions, not for time-based lookups. We just need to find the right time series that are relevant for your query. As a simple example, we have one LevelDB index which has single label=value pairs as the keys and as the LevelDB value, the identifiers of the time series which have those label=value dimensions. If you now query for e.g. all time series with labels foo="biz" AND bar="baz", we will do two lookups in that index: one for the key foo="biz", and one for bar="baz". We will now have two sets of time series identifiers which we intersect (AND-style matching) to arrive at the set of time series you're interested in querying. Only then do we actually start loading any actual time series data (not from LevelDB this time).