We're scaling toward Series A, launching our productized platform in 2026, and publishing original cryptographic research alongside the product. We're hiring a Staff Engineer to design and ship the custody platform's hardest backend code. This is a hands-on IC role with real technical leadership — no people management — where you drive non-trivial initiatives through code, RFCs, and mentorship. We're AI-forward (Claude Code, Cursor, Codex), and we need engineers who can read AI-generated code critically and catch what it misses — not just prompt it. You'll naturally gravitate toward either the security-critical core (MPC, threshold signing, HSM/Ledger integration, key lifecycle) or the faster-moving periphery (chain adapters, integrations, APIs/SDKs). Security-by-design: least privilege, secret handling, mTLS/JWT, tamper-evident logs, audit-ready data models — designed for SOC 2, ISO 27001, and DORA scope from day one. Performance & data: profiling, load testing, benchmarking, contention analysis, GC tuning; contribute to the company's AI engineering practices; Set patterns and shared libraries for the services your area touches; raise the bar through code review and example.



Own features end-to-end: design notes / RFCs, code, tests, observability, rollout, on-call. No "throw it over the wall" handoffs. Mentor senior engineers: your reviews and your written designs are the strongest signal to the rest of the team. 10+ years backend engineering, including 3+ years operating at Staff level (or equivalent senior IC scope). Strong production experience in a modern systems language — Go, Rust, Java, C++, or comparable. Hands-on Go experience, or genuine readiness to ramp on Go in the first month. ~ Proven track record building high-load, multi-tenant SaaS in production (HA, incident response, SLOs). ~ Hands-on with modern backend stacks: gRPC/ queues/streams, caching, relational databases, Kafka/NATS or equivalent. ~ Exposure to custody, wallets, or signing systems (MPC, HSM, TEE, key management, approvals). Regulated-environment experience (fintech, security audits, compliance-driven engineering). Benefits Fully remote, any time zone with reasonable overlap with EU/CIS hours. full benefits.

📌 Senior Staff Backend Engineer (España)
🏢 The Vault
📍 España