Added IE support to a web application that relied on web SQL by pollyfilling sqlite using asm.js. It was pretty slow, but it gave us enough breathing room to eventually replace web SQL with a local storage based implementation.

That was also slow, but was able to speed it up by using compound keys and binary search to do range queries of "tables" based on key prefixes (the bulk of the data was time series/event like)

Wasn't able to use indexeddb at the time due to compatibility issues as far as I recall.