Staff Backend Engineer

As a Staff Backend Engineer at The Vault, you design and ship the hardest backend code for an MPC-based crypto custody platform scaling toward Series A. 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. You'll own either the security-critical core (MPC, threshold signing, HSM/Ledger integration, key lifecycle) or the faster-moving periphery (chain adapters, integrations, APIs/SDKs), shaping architecture in your area while platform-wide decisions sit with technical leadership.

What you'll do

• Design, write, and ship critical platform components including the policy engine, signing orchestration, key lifecycle workflows, recovery flows, approvals, audit trails, and multi-tenant wallet and account services
• Lead non-trivial cross-cutting initiatives in your area through written RFCs, design reviews, and code, not through hierarchy
• Build high-load, multi-tenant SaaS systems with tenant isolation, quotas, rate limits, backpressure, concurrency control, and predictable latency under spikes
• Apply distributed systems and reliability patterns: idempotency, retries, outbox/inbox, event-driven workflows, sagas and state machines, replay, and graceful degradation
• Implement security-by-design practices including least privilege, secret handling, mTLS/JWT, tamper-evident logs, and audit-ready data models designed for SOC 2, ISO 27001, and DORA from day one
• Drive performance and data excellence through profiling, load testing, benchmarking, contention analysis, and GC tuning; build strong relational models with Postgres or equivalent, handle migrations and indexing, and define clear consistency boundaries
• Ship production code with Claude Code, Cursor, and Codex as a core competency; build prompt and agent patterns for your area; know when to use AI heavily (periphery, integrations, tests, docs) and when not to (cryptographic core, signing paths) where blind generation is unsafe
• 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, and on-call-no handoffs
• Mentor senior engineers; your reviews and written designs are the strongest signal to the rest of the team

What you bring

• Strong CS fundamentals: you reason from first principles about concurrency, distributed systems, consistency models, networking, and OS behaviour. You know not just what locks and channels do, but why and when
• Ownership mindset: you have owned non-trivial production systems end-to-end-design, ship, measure, improve, on-call-and you don't wait to be told what to do
• 10+ years of backend engineering, including 3+ years operating at Staff level or equivalent senior IC scope, with strong production experience in a modern systems language such as Go, Rust, Java, or C++. Hands-on Go experience, or genuine readiness to ramp on Go in the first month
• Track record of Staff-level technical leadership through code, RFCs, and influence without formal authority. You can point to RFCs you wrote that the team adopted and initiatives you drove without being the manager
• Proven track record building high-load, multi-tenant SaaS in production with HA, incident response, and SLOs
• Hands-on experience with modern backend stacks: gRPC/HTTP, queues/streams, caching, relational databases, Kafka/NATS or equivalent
• Strong testing discipline: unit, integration, and contract tests with testability-first design and deterministic CI
• Strong observability habits: structured logging, metrics, tracing, and end-to-end production debugging
• Production-grade use of modern AI coding tools (Claude Code, Cursor, Codex, or comparable). You read AI-generated code as a hostile reviewer, you have instincts for what AI tends to get wrong, and you don't ship code you couldn't have written yourself

Nice to have

• Exposure to custody, wallets, or signing systems such as MPC, HSM, TEE, key management, and approvals
• Hardware wallet integration experience with Ledger
• Multiple blockchain ecosystems: EVM and Bitcoin minimum, with Cosmos, Solana, or others a plus
• Custom agents, MCP integrations, or in-repo AI workflows that compounded a team's productivity
• Designed and run evals for AI-generated code covering correctness, security, and style
• Kubernetes and service mesh in production, with SRE practices
• Regulated-environment experience in fintech, security audits, or compliance-driven engineering
• Threat modelling and security review participation
• Familiarity with SOC 2, ISO 27001, and DORA enough to design for them

What we offer

• A Staff IC role with real technical leadership, no people management, and no sprint mechanics gauntlet
• An AI-forward engineering culture with budget and autonomy for the tooling, models, and agents you need
• Direct peers in cryptography research, security architecture, product, and delivery
• Fully remote, any time zone with reasonable overlap with EU/CIS hours
• Competitive compensation at the Staff engineer band, equity participation, and full benefits
• A product approaching Series A with paying institutional customers and a published cryptographic research line

About The Vault

The Vault is an MPC-based crypto custody platform for institutional and retail clients, running threshold signing across HSM and Ledger hardware. Scaling toward Series A, the company is launching its productized platform in 2026 and publishing original cryptographic research alongside the product.