Month 5 Capstone: Production FastAPI Microservice, Streaming Chatbot & MLOps Platform

1. Executive Summary & Production Blueprint

This Month 5 Capstone represents the complete production enterprise wrapper around our Month 1–4 foundational engines (SRE CLI, Evaluator Suite, Hybrid RAG, and Agentic MCP Server).

It exposes an enterprise-grade REST microservice combining:

Asynchronous Non-Blocking High Concurrency: Built on FastAPI & ASGI (Uvicorn), serving thousands of simultaneous requests.
Server-Sent Events (SSE) Multiplexing: Streaming thought, component, token, citation, and done frames.
Multi-Turn Chat Memory & Bounded Context: Sliding window token manager with background compaction.
Tenant Security & Token-Bucket Rate Limiter: Guarding against Denial-of-Wallet (DoW) attacks via RPM burst limits and daily dollar caps.
Sub-10ms Semantic Prompt Caching: Vector similarity matching ( $\theta \ge 0.95$ ) returning cached incident answers at $0.00 cost.
Resilient Cascade Fallback Gateway: Zero-downtime routing from Primary (OpenAI gpt-4o-mini) to Secondary (Anthropic claude-3-5-haiku) on 429/503 errors.
OpenTelemetry & Langfuse Observability: Full distributed trace context with W3C traceparent propagation and Prometheus /metrics exposition.
Hardened Multi-Stage Container: Minimal non-root container (USER 10001) with cgroup limits and automated Kubernetes probes (/healthz, /readyz).

2. Architecture & Data Flow

Architecture Flow Diagram

Client (Browser / Python SDK / CLI)->|POST /v1/copilot/query| Auth[1. API Key Auth & Token-Bucket Rate Limiter

Quota{2. Spend Quota Check}

|Exceeded| Reject[HTTP 429 / 402 Error

|OK| Cache{3. Semantic Cache (Cosine >= 0.95)}

|Hit (< 10ms, $0.00)| CacheReturn[Instant SSE Token Stream

|Miss| GW[4. Resilient Cascade Model Router

P1[Primary: OpenAI gpt-4o-mini

|503 Outage| P2[Fallback: Claude 3.5 Haiku

& P2->Store[5. Store in Semantic Cache + Bounded Memory

OTel[6. Emit OpenTelemetry GenAI Span (W3C traceparent)

LF[7. Export Langfuse Observability Trace

Prom[8. Prometheus /metrics & K8s Health Probes

3. Microservice Endpoints Specification

Method	Endpoint	Description	Expected Output
`GET`	`/healthz`	Kubernetes Liveness Probe	`{"status": "alive", "uptime": 42.1}`
`GET`	`/readyz`	Kubernetes Readiness Probe	`{"ready": true, "dependencies": {...}}`
`GET`	`/v1/copilot/metrics`	Prometheus Metrics Exposition	Plain-text Prometheus counters, gauges, histograms
`POST`	`/v1/copilot/query`	Streaming SSE & JSON Copilot Query	`text/event-stream` (thought, token, component, citation, done)
`POST`	`/v1/copilot/feedback`	User Feedback Scoring	`{"status": "recorded", "score": 1.0}`