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 serving institutional and retail clients. This is a hands-on individual contributor role with real technical leadership-no people management-where you drive non-trivial initiatives through code, RFCs, and mentorship. You'll shape architecture in your area of ownership, working with threshold signing across HSM and Ledger hardware as the company scales toward Series A and launches its productized platform in 2026.

What you'll do

• Design, write, and ship critical platform components: policy engine, signing orchestration, key lifecycle workflows, recovery flows, approvals, audit trails, 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: tenant isolation, quotas, rate limits, backpressure, concurrency control, predictable latency under spikes
• Own distributed systems and reliability: idempotency, retries, outbox/inbox patterns, event-driven workflows, sagas and state machines, replay, graceful degradation
• Design security from the ground up: least privilege, secret handling, mTLS/JWT, tamper-evident logs, audit-ready data models-built for SOC 2, ISO 27001, and DORA scope from day one
• Drive performance and data work: profiling, load testing, benchmarking, contention analysis, GC tuning; strong relational modelling with Postgres or equivalent, migrations, indexing, clear consistency boundaries
• Use AI-assisted development as a core competency: ship production code with Claude Code, Cursor, and Codex; build prompt and agent patterns that work for your area; contribute to the company's AI engineering practices; 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 and RFCs, code, tests, observability, rollout, on-call
• 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 understand what's happening under the hood, not only at the API level
• Ownership mindset: you've owned non-trivial production systems end-to-end (design, ship, measure, improve, on-call); you don't wait to be told what to do, and you don't ship code you don't understand
• 10+ years backend engineering, including 3+ years 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
• 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, initiatives you drove without being the manager, patterns you set that outlasted you
• Proven track record building high-load, multi-tenant SaaS in production (HA, incident response, SLOs)
• Hands-on with modern backend stacks: gRPC/HTTP, queues/streams, caching, relational databases, Kafka/NATS or equivalent
• Strong testing discipline: unit, integration, and contract tests; testability-first design; deterministic CI
• Strong observability habits: structured logging, metrics, tracing, end-to-end production debugging
• Production-grade use of modern AI coding tools (Claude Code, Cursor, Codex, or comparable); you can point at what you've built with them; you read AI-generated code as a critical reviewer, not a grateful recipient; 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 (MPC, HSM, TEE, key management, approvals)
• Hardware wallet integration (Ledger)
• Multiple blockchain ecosystems (EVM and Bitcoin minimum; Cosmos, Solana, others a plus)
• Built custom agents, MCP integrations, or in-repo AI workflows that compounded a team's productivity
• Designed and run evals for AI-generated code (correctness, security, style)
• Kubernetes and service mesh in production; SRE practices
• Regulated-environment experience (fintech, security audits, 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, no sprint mechanics gauntlet, no architecture-by-committee
• 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, 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. The company is scaling toward Series A, launching its productized platform in 2026, and publishing original cryptographic research alongside the product.