8.4.1 Engineering Roadmap: Async, API, Logs, Deploy

Engineering turns a working LLM demo into software that can be deployed, debugged, measured, and maintained after prompts, models, documents, and users change.

See the LLMOps Loop First

Your first engineering goal is simple: when an answer is wrong, you can explain which layer caused it.

Run a Trace Readiness Check

Every production-style LLM feature needs enough trace fields to debug one bad answer.

trace = {
    "request_id": "demo-001",
    "prompt_version": "rag-v2",
    "retrieval_hits": 2,
    "model_ms": 850,
    "format_ok": True,
    "cost_usd": 0.003,
}

required = ["request_id", "prompt_version", "retrieval_hits", "model_ms", "format_ok", "cost_usd"]

print("trace_ready:", all(field in trace for field in required))
print("debug_fields:", ", ".join(required))

Expected output:

trace_ready: True
debug_fields: request_id, prompt_version, retrieval_hits, model_ms, format_ok, cost_usd

If these fields are missing, debugging becomes guesswork. Add logs before adding more features.

Learn in This Order

Step	Read	Practice Output
1	Async programming	Add timeout, retry, concurrency limit, and cancellation thinking
2	API design	Define request/response schema and error codes
3	Logging and monitoring	Record prompt version, retrieval hits, latency, cost, and failures
4	Docker deployment	Package the app with reproducible run instructions

Evidence to Keep

Keep this page’s proof of learning as a small evidence card:

Service Contract

endpoint, input schema, output schema, error schema

Run Signal

latency, throughput, logs, health check, or container status

Observability

request id, trace id, structured log, or metric

Failure Check

timeout, retry storm, missing log, deployment mismatch

Ops Action

backoff, queue, alert, rollout, or rollback

Pass Check

You pass this chapter when your minimal app has a run command, API contract, error handling, logs, and one documented failure investigation.

The exit mini project is an engineering evidence pack: one trace log, one common error, one fix, one regression check, and one deployment note.

Check reasoning and explanation

1. A passing answer traces the full path from query to chunks, retrieval scores, cited evidence, answer, and fallback behavior.
2. The evidence should include retrieved passages, source metadata, a cited answer, and at least one empty-retrieval or wrong-retrieval case.
3. A good self-check explains whether a failure came from chunking, retrieval, ranking, prompt assembly, missing sources, or unsupported generation.