Docker

You can self-host a private PyPI registry with pypiserver and a private npm registry with Verdaccio . Both run on a single box or inside Docker containers. You get three wins that public registries cannot match: faster installs from a LAN cache, a safe home for private packages, and cover against outages, typosquatting, and supply chain attacks. Both tools are free, open-source, and take under 30 minutes to set up.

Testcontainers spins up real databases and services as Docker containers inside your test suite. Tests run against production-grade PostgreSQL, Redis, or Kafka instead of flaky mocks. The testcontainers-python v4.14.2 library works with pytest . It automates the container life cycle. You get isolated, reproducible integration tests that catch bugs unit tests miss.

Below: setup with pytest, testing services beyond databases, performance patterns, and CI/CD configuration.

Why Mocks and In-Memory Databases Are Not Enough

Mocking db.execute() only checks if your code calls the function. It does not check if the SQL is valid. It also misses schema errors and type mismatches. You might have passing tests while your queries fail in production.

You can unify access to Ollama, vLLM, cloud providers like OpenAI, Anthropic, and Google, plus custom model servers behind one OpenAI-compatible endpoint using LiteLLM Proxy . LiteLLM is a reverse proxy. It maps the standard /v1/chat/completions request to each provider’s native API. From one YAML file it handles auth, model routing, load balancing, fallbacks, rate limits, and spend tracking. Your app calls one endpoint with one key, and LiteLLM picks the right backend. You can swap models, add providers, or run A/B tests without touching app code.

You can expose a local dev server to webhooks from GitHub, Stripe, or Twilio. Run cloudflared next to a FastAPI app. This drops port forwarding, public IPs, and paid ngrok plans. Cloudflare Tunnels open an outbound-only encrypted link from your machine to Cloudflare’s edge. The edge then proxies webhook requests back to your local FastAPI endpoint with full TLS, auto reconnect, and no firewall changes.

The trick works because cloudflared opens QUIC connections outward from your machine. No inbound ports ever open on your router. Cloudflare’s edge gets the webhook POST from GitHub or Stripe. It routes that POST through your tunnel and hands it to localhost:8000, where FastAPI handles it. You get a stable, public URL like webhooks.yourdomain.com that survives reboots.

Pair Meilisearch v1.12’s fast REST API with HTMX 2.0’s hx-get and hx-trigger attributes, and you get a real-time, typo-tolerant search box that returns results in under 50ms. You write no custom JavaScript and pull in no React or Vue. The server renders HTML fragments that HTMX swaps into the DOM, so the whole search box stays under 15 KB of total JS. This post covers the full setup, from Docker Compose to a working search UI with faceted filtering.

You can build a fully local, sandboxed code interpreter agent. You pair Ollama (running a reasoning model such as Scout, the smallest Llama 4 variant , or DeepSeek R1) with a Docker container that runs the generated Python code. The agent sends a prompt to the local LLM, which writes Python. That code goes into a locked-down container with no network and strict limits. The output feeds back to the LLM so it can fix and retry. The whole loop runs on your machine with zero cloud calls.