Training code is product code
Use training code is product code to move the engineering foundations production brief toward a defensible release.
A churn notebook cannot be reproduced by the teammate expected to ship it.
This lesson isolates training code is product code as one decision inside that system. The people affected are product users and operators; the learning data must carry event time, availability time, ownership, and version; and the operating envelope is a declared latency, cost, and operator-capacity budget.
Choose whether and how to use dependency locks at a declared prediction cutoff.
Measure decision utility alongside calibration, slice reliability, and system latency—not model score alone.
A churn notebook cannot be reproduced by the teammate expected to ship it. An unsafe release must degrade to a named baseline or the last known-good version.
Build the mental model before the machinery.
The core move is to treat training code is product code as a contract between data, a computation, and an action. Reject promotion when any artifact lacks lineage, golden raw-request parity, or a failure-safe recovery path. The implementation becomes easier to debug once you can state which inputs exist, which state is learned, what output means, and what must remain invariant after serialization.
dependency locks
Define it in a hand-checkable form and name the prediction-time inputs.
run manifests
Connect it to the production metric and identify what it cannot guarantee.
schema contracts
Stress it with a slice, a temporal boundary, and a failure-safe alternative.
golden inference
Stress it with a slice, a temporal boundary, and a failure-safe alternative.
Lessons 1, 2 in this course.
Name every symbol. Check every shape.
Content-addressed run identity is the central invariant for this lesson. The formula is useful only when its inputs match the production cutoff and its output maps to an action.
Content-addressed run identity
| Symbol | Meaning / shape / unit |
|---|---|
code | source revision digest |
data | immutable dataset digest |
image | OCI image digest |
seed | declared random seed |
Open derivation and numerical substitution
Start from the production quantity being optimized, substitute the observed values with their declared units, then isolate the model-controlled term. Preserve shape annotations at each step so broadcasting or aggregation cannot silently change the result.
- Write the named inputs: code, data, image, seed.
- Substitute one small, hand-checkable batch before vectorizing.
- Calculate an independent reference value and compare within a declared tolerance.
# equation → code contract
inputs = validate_shapes_and_units(batch)
value = compute_c01(inputs)
assert is_finite(value)Calculate it small. Shape it realistically. Break it on purpose.
A result you can reproduce on paper
Fit the same line twice from four rows, one locked environment, and one seed; compare manifests and predictions.
- Write every input and unit.
- Substitute values into the content-addressed run identity equation above.
- Compare the result to one simple baseline and explain the direction of the difference.
The same reasoning under real constraints
A nightly churn run records source commit, Parquet snapshot, image digest, feature version, metrics, and artifact checksum.
The production record includes the data snapshot, transformation state, artifact identity, cutoff, score, decision, and the version of the policy that consumed it.
The attractive result you should reject
A mutable data/latest path and unpinned dependencies create a different model from the same command.
Diagnostic: replay the smallest failing slice from immutable inputs, then compare each boundary rather than retuning the model.
Change one assumption and make the tradeoff visible.
This lab runs predefined TypeScript only. It never executes learner code. Use the slider, numeric input, reset, live text, or table—the computation is the same.
Reproducibility fault injector
Change how many declared inputs remain mutable and observe replay parity.
Assumption: Each mutable input independently creates a 14-point replay risk.
Open nonvisual data table
| Item | Computed state | Interpretation |
|---|---|---|
| input 1 | mutable | replay risk |
| input 2 | mutable | replay risk |
| input 3 | content-addressed | verified |
| input 4 | content-addressed | verified |
| input 5 | content-addressed | verified |
Trace the complete operating path.
- 01
Validate and version dependency locks.
- 02
Compute training code is product code from prediction-time-safe inputs.
- 03
Persist model, feature, and configuration identities together.
- 04
Serve or materialize behind explicit a declared latency, cost, and operator-capacity budget.
- 05
Join telemetry to mature outcomes and retain a rollback path.
Observability
Join service health, input quality, prediction distributions, slice behavior, and mature outcomes by exact version.
Cost
Measure storage, preprocessing, compute, queueing, and human review under a representative arrival pattern.
Failure modes
A mutable data/latest path and unpinned dependencies create a different model from the same command. Add a detector, owner, mitigation, and stop condition for this class of failure.
Alternatives
Compare a rule, a simpler statistical baseline, and a different system boundary before adding model complexity.
Explain the contract, not just the vocabulary.
Reproducible baseline package
Design a Docker-only workflow that validates data, trains, evaluates, serializes, performs golden inference, and emits complete lineage.
- Run manifest and data contract
- Raw-input golden parity test
- Failure and retry runbook
- Model card with residual nondeterminism
Read primary material with a purpose.
Return to the opening failure.
Reject promotion when any artifact lacks lineage, golden raw-request parity, or a failure-safe recovery path.
For this lesson, the release evidence is a hand-checked formal result, deterministic simulation output, a ≥80% checkpoint, the production rubric, and a named fallback. The course resolves when the system can produce a seeded, tested, packaged, versioned training workflow with a model card.