Electrum address syncronization
Electrum wallet requires a special Electrum compatible server where it can query the data needed.

There are now several implementations eg:


https://github.com/spesmilo/electrum-server
https://github.com/chris-belcher/electrum-personal-server
https://github.com/kyuupichan/electrumx



  ...code snippet that implements such funtionality


https://github.com/spesmilo/electrum-server/blob/ce1b11d7f5f7a70a3b6cc7ec1d3e552436e54ffe/src/storage.py#L286