River

River is a client-first Bitcoin-only financial institution building the financial app people use every day to save in bitcoin and spend in dollars. They custody over 25,000 BTC, serve individuals and businesses across the U.S., and are profitable. They publish cryptographic proof of reserves monthly and release company financials annually. The engineering team works on: real-time Bitcoin and USD payments/trading/settlement on an Elixir monolith with unified GraphQL API; next-generation Bitcoin custody with quorum signing, key ceremonies, and geo-redundant infrastructure; scaling ML/AI systems (Python, PyTorch, XGBoost, LLMs) to automate operations and tackle fraud/risk; ground-up React and React Native rewrite of the consumer app; porting Lightning Network infrastructure from Go into Elixir. Hiring: Staff Software Engineer (Elixir); Senior Software Engineer (React, Full-stack); Senior/Staff Machine Learning Engineer.