I submitted this as a pull-request (see #91) but it appears not much is happening with that repo right now, so here is the essential part of my pull request for anyone to use.
The original idb-keyval opens a new transaction for every (
del) operation, which is inefficient for performing lots of opertations. One alternative is to use a more full-featured library like IDB or Dexie, which feature batch operations that perform several in the same transaction.
This mod maintains the original i