Senior Software Engineer, Custody

ProspeX CRM is a digital-asset custody and infrastructure platform for the GCC. They are seeking a senior backend engineer with custody and key-management experience to work on their custody platform, handling signing service, key management, chain integrations, and transaction pipeline.

• Ship production custody code across signing service, key management, chain integrations, and the transaction pipeline.
• Own a chain or a subsystem. Within 3 months you should own a meaningful surface end-to-end (a chain integration, a signing-service component, a key-rotation flow).
• Pair with the Custody Platform Lead and our in-house cryptography function on threshold signing, share generation, and key recovery flows.
• Write post-mortems when things break. We treat these as architecture-improvement opportunities, not blame exercises.
• Integrate new chains. Bitcoin, Ethereum and L2s, Solana, and an active onboarding queue.
• Engage in async written communication. Spec docs, PR descriptions, async design reviews.

• 5-plus years of backend engineering, with the last 2-plus years on a custody platform or a key management system at a regulated entity. General fintech does not substitute.
• Hands-on with at least one of: HSM lifecycle (CloudHSM, YubiHSM, Ledger Vault, similar). MPC / TSS (Fireblocks-style, Sepior, ZenGo, Curv-style). Threshold signing schemes (GG18, GG20, FROST, CGGMP21, CMP).
• Production experience with one or more of: Bitcoin (UTXO model, PSBT). Ethereum (EIP-712, EIP-1559, account abstraction). At least one non-EVM Layer 1 (Solana, Sui, Cosmos SDK chain, similar).
• Reads Solidity, Move, or Rust well enough to integrate with new chains without hand-holding.
• Strong async written communication. Your PR threads, design docs, and intro reply are themselves a signal.
• English fluency.