Senior Backend / Platform Engineer

You'll own the platform our agents run on — event-driven architecture, data pipelines, integrations with customer accounting systems, and the infrastructure that makes everything reliable, auditable, and fast. What you'll do - Event store — Append-only PostgreSQL with tamper-evident hash chaining, real-time event distribution, agent replay and recovery, schema versioning. - Cryptographic signature infrastructure — Key management, signature verification on all agent events, approval chains for external actions. - Workflow Constraint Engine — The gateway that verifies authorization before any external action (email, payment, API call) proceeds. - PII Vault & GDPR compliance — Isolated, encrypted storage for personal data. Right to erasure. Data residency per region. - Multi-tenancy — Row-level security, tenant isolation across all data stores, tenant-scoped LLM API keys. - Authorization (Cerbos) — Attribute-based access control for agents and humans. Deterministic policy evaluation — LLMs never make auth decisions. - MCP security layer — Authentication, capability-based scoping per partner, and rate limiting for the Model Context Protocol endpoint. - Database architecture — PostgreSQL schema design, indexing strategy, performance tuning, read replica topology. What we're looking for - 3+ years experience with Python and/or TypeScript in production. - 5+ years designing backend platforms for production systems. - Strong systems design skills — this is the primary requirement. You think in boundaries, contracts, failure modes, and scaling characteristics. - Deep PostgreSQL knowledge — RLS, indexing tradeoffs, event sourcing patterns, schema evolution. - Strong application security architecture skills: encryption models, key management, auth patterns. - Experience with policy-as-code authorization (Cerbos, OPA, Cedar, or similar). - Strong code review skills for security-sensitive AI-generated code. - Nice to have: - Cryptographic primitives in production (digital signatures, hash chaining, application-layer encryption). - Event streaming platforms (Kurrent, Redpanda, Kafka). - SOC 2 or GDPR compliance engineering. - Fintech or regulated-environment background.