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.