Senior SaaS Architect & Principal Backend Engineer (FastAPI, AI Agents, Multi-Tenant SaaS, MCP)

We are building an AI-powered automation platform for small and medium-sized businesses. Our platform automates customer communication, bookings, CRM workflows, WhatsApp conversations, knowledge-base retrieval, AI-assisted responses, and business operations. The architecture is already significantly developed and includes: FastAPI PostgreSQL SQLAlchemy Async Redis Celery Multi-Tenant RLS Architecture MCP Router Architecture AI Agent Runtime Knowledge Base / RAG Layer WhatsApp Integration Next.js Frontend The system is currently entering pilot-customer onboarding. We are looking for a senior technical reviewer who can independently audit architecture decisions, identify weaknesses, challenge assumptions, and help prepare the platform for real-world production usage. This is NOT a junior or mid-level implementation role. We are looking for someone who has designed and operated SaaS products at scale. What We Need We want a deep technical review covering: Architecture: Multi-tenant architecture Tenant isolation RLS strategy Service boundaries Event-driven design Scalability assumptions Failure handling AI Runtime: Agent orchestration MCP architecture Tool routing Approval workflows Human handover flows Knowledge retrieval Infrastructure: Production readiness Reliability Monitoring Logging Alerting Security Data Layer: PostgreSQL design Migration strategy Indexing Query efficiency Long-term maintainability Security & Compliance: GDPR Consent handling Multi-tenant isolation Access control Ideal Candidate You have experience with: FastAPI PostgreSQL SQLAlchemy Redis Celery Distributed systems SaaS architecture Multi-tenant systems Event-driven systems AI agent platforms Production-scale software Bonus: MCP experience RAG systems LangGraph OpenAI integrations WhatsApp Business API European SaaS products Deliverables We expect: Architecture Review Risk Assessment Scalability Review Security Review Production Readiness Review Written Recommendations Prioritized Action Plan We appreciate disagreement and critical thinking. Do not tell us what we want to hear. Tell us what could break. To Apply Please answer: What is the largest SaaS platform you have architected? Have you designed multi-tenant systems with PostgreSQL RLS? Have you worked with FastAPI in production? Have you built or reviewed AI agent systems? What architectural mistake do you see most often in startup SaaS products? What would you review first in a platform like ours? Please include examples of systems you have personally designed. We are looking for long-term collaboration with the right person.