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Capstone Brief — The Admission Service

advanced12 min readLesson 202 of 204

One spec, one acceptance battery: per-tag admission with windows and provenance, plus an exact ops report. You ship when the battery is green.

The brief

You are the engineer of record for an admission service core. There is no tutorial for this module — the acceptance battery is the specification.

AdmissionsCore — tag-scoped admission over a deterministic clock:

  • setTagLimit(tag, limit) accepts only tag >= 0, limit >= 1, and only the first configuration of a tag (re-setting fails, returns false).
  • admit(cls, tag) — unknown tags are rejected; a tag admits while its in-window usage is under its limit; the winner gets its arrival ordinal within the tag for the current window.
  • A window is a single clock timestamp: the first admit at a new timestamp rolls per-tag counters and ordinals.
  • Running totals: admittedCount(), rejectedCount().

OpsReport — the audit trail, graded as an exact string:

  • record(tMs, code, key) then snapshot() produces "[ts] CODE key\n" lines, oldest timestamp first; at equal timestamps, REJECT sorts before ADMIT (an audit reads failures first).
  • Determinism contract: same calls, same clock, byte-identical snapshot.

Everything from this course converges here: the clock seam (M19), per-key state with clear ownership (M6/M11), exact-string reporting (M20), and the two-sided testing discipline (M15).