• Efficient, lightweight reimplementation of electrum-server

  • Fast synchronization of ravencoin mainnet from Genesis. Recent hardware should synchronize in well under 24 hours. The fastest time to height 448k (mid January 2017) reported is under 4h 30m. On the same hardware JElectrum would take around 4 days and electrum-server probably around 1 month.

  • Various configurable means of controlling resource consumption and handling bad clients and denial of service attacks. These include maximum connection counts, subscription limits per-connection and across all connections, maximum response size, per-session bandwidth limits, and session timeouts.

  • Minimal resource usage once caught up and serving clients; tracking the transaction mempool appears to be the most expensive part.

  • Mostly asynchronous processing of new blocks, mempool updates, and client requests. Busy clients should not noticeably impede other clients’ requests and notifications, nor the processing of incoming blocks and mempool updates.

  • Daemon failover. More than one daemon can be specified, and ElectrumX will failover round-robin style if the current one fails for any reason.

  • Peer discovery protocol removes need for IRC

  • Coin abstraction makes compatible altcoin and testnet support easy.


ElectrumX does not do any pruning or throwing away of history. I want to retain this property for as long as it is feasible, and it appears efficiently achievable for the foreseeable future with plain Python.

The following all play a part in making it efficient as a Python blockchain indexer:

  • aggressive caching and batching of DB writes

  • more compact and efficient representation of UTXOs, address index, and history. Electrum Server stores full transaction hash and height for each UTXO, and does the same in its pruned history. In contrast ElectrumX just stores the transaction number in the linear history of transactions. For at least another 5 years this transaction number will fit in a 4-byte integer, and when necessary expanding to 5 or 6 bytes is trivial. ElectrumX can determine block height from a simple binary search of tx counts stored on disk. ElectrumX stores historical transaction hashes in a linear array on disk.

  • placing static append-only metadata indexable by position on disk rather than in levelDB. It would be nice to do this for histories but I cannot think of a way.

  • avoiding unnecessary or redundant computations, such as converting address hashes to human-readable ASCII strings with expensive bignum arithmetic, and then back again.

  • better choice of Python data structures giving lower memory usage as well as faster traversal

  • leveraging asyncio for asynchronous prefetch of blocks to mostly eliminate CPU idling. As a Python program ElectrumX is unavoidably single-threaded in its essence; we must keep that CPU core busy.

Python’s asyncio means ElectrumX has no (direct) use for threads and associated complications.


  • break ElectrumX up into simple services that initially can be run in separate processes on a single host. Then support running them on different hosts, and finally support sharding. With this we can take advantage of multiple cores and hosts, and scale to much larger block sizes. This should solve several issues with the current history storage mechanism.

  • fully asynchronous operation. At present too much is synchronous, such as file system access.

  • protocol improvements targeting better client and server scalability to large wallets (100k addresses) and address histories. Some aspects of the current protocol are very inefficient.

  • investigate speaking the Ravencoin protocol and connecting to the Ravencoin network directly for some queries. This could lead to ElectrumX being runnable with a node without a tx index, or a pruning node, or not needing to run a node at all. ElectrumX would store all blocks itself and index the transactions therein.

  • lifting internal limits such as maximum 4 billion transactions

  • supporting better user privacy. I believe significantly improved user address privacy might be possible with a simple addition to the protocol, and assuming a server network of which a reasonable fraction (40%?) are cooperative and non-colluding

  • new features such as possibly adding label or wallet server functionality