FastAPI Observability : Correlation IDs & ContextVars (2026)

<h2> The Problem: One Request, Five Services, Zero Clues </h2> <p>A user reports that "saving their profile failed." You open your logs and find a <code>500</code>. But that

<p>When we build backend systems, especially APIs and microservices, debugging production issues is rarely about reading one log line.</p> <p>A single request may pass through an

<p>I'm rebuilding <strong>evorag</strong>, a Python retrieval service: it chunks documents, embeds them with OpenAI's <code>text-embedding-3-small</code>, stores vectors in

<blockquote> <p>For full observability in FastAPI you need 6 pip packages + 60 lines of config + manual glue between logs/spans/metrics. In Fitz it's two decorators and an env