# noCV engineering task library Content version 5 Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs. Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence. ## CAUCT — A realtime reservation window for workshop seats Fictional craft studio Maple offers workshop seats. Implement synthetic reservations without payments or real booking services. **Field:** Real-time systems. **Suggested stack:** TypeScript, PostgreSQL adapter, WebSocket, Vitest. **Engineer value:** Practice contention, expiry and truthful realtime projections. **Company value:** Inspect whether concurrent clients avoid overselling and recover uncertain results. **Delivery agreement:** Booking simulation only; payment and production capacity planning are excluded. ### Setup prerequisites - Create synthetic workshops with small capacities. - Implement local transactional hold storage and injected clocks. ### Define hold rules Specify capacity and ownership. #### CAUCT-101 — Specify workshop seat counts without negative availability **Task · High priority · Foundational** noCV practice brief v5 · CAUCT-101 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define hold rules. Depends on: No preceding ticket. Difficulty: Foundational. Estimated focused work: 75 minutes; setup and prerequisite tickets are additional. Estimated field mix: Backend 60% · Database engineering 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. The prototype subtracts all historical holds and displays negative seats. Project availability from current authoritative states. Acceptance criteria - Only active holds consume seats - Confirmed reservations consume seats - Expired holds do not consume seats Implementation constraints - Define active using injected time. Verification - Project mixed states - Use boundary expiry instant Deliverables - Availability projection and cases Rollout and recovery: Hide counts if state cannot be reconciled. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CAUCT-102 — Validate workshop hold quantities before storage **Bug · Medium priority · Foundational** noCV practice brief v5 · CAUCT-102 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define hold rules. Depends on: CAUCT-101. Difficulty: Foundational. Estimated focused work: 60 minutes; setup and prerequisite tickets are additional. Estimated field mix: Backend 80% · API design 20%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. A zero-seat request creates a hold and a fractional request breaks counts. Enforce bounded integer quantities. Acceptance criteria - Positive integers within limit pass - Zero and fractions fail - Invalid input creates no record Implementation constraints - Keep limits explicit in the local contract. Verification - Hold two seats - Reject zero and oversized quantities Deliverables - Quantity validator and failure cases Rollout and recovery: Reject new holds if validation is unavailable. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CAUCT-103 — Create workshop holds atomically under contention **Task · High priority · Advanced** noCV practice brief v5 · CAUCT-103 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define hold rules. Depends on: CAUCT-101, CAUCT-102. Difficulty: Advanced. Estimated focused work: 180 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 70% · Backend 30%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Two clients see one available seat and both reserve it. Serialize capacity consumption at storage. Acceptance criteria - At most capacity is consumed - Loser receives unavailable result - No partial hold record remains Implementation constraints - A browser availability check is advisory only. Verification - Create uncontested hold - Race two requests for one seat Deliverables - Transactional hold operation Rollout and recovery: Pause hold creation if capacity invariant fails. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. ### Resolve concurrent changes Handle expiry and confirmation atomically. #### CAUCT-104 — Scope workshop hold lookup and cancellation to its owner **Bug · High priority · Intermediate** noCV practice brief v5 · CAUCT-104 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Resolve concurrent changes. Depends on: CAUCT-103. Difficulty: Intermediate. Estimated focused work: 135 minutes; setup and prerequisite tickets are additional. Estimated field mix: Security 70% · Backend 30%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Knowing a hold ID lets another user cancel it. Enforce owner scope in the repository boundary. Acceptance criteria - Owner reads and cancels - Foreign owner is denied - Denied calls do not disclose hold details Implementation constraints - Synthetic identities remain required in all adapter calls. Verification - Cancel own hold - Cancel another account's hold Deliverables - Scoped hold repository and denial tests Rollout and recovery: Disable cancellation if scope cannot be established. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CAUCT-105 — Confirm workshop holds only before the expiry boundary **Task · High priority · Advanced** noCV practice brief v5 · CAUCT-105 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Resolve concurrent changes. Depends on: CAUCT-103, CAUCT-104. Difficulty: Advanced. Estimated focused work: 180 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 60% · Backend 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Confirm and expiry cleanup race, creating reservations from expired holds. Add an atomic transition with one time rule. Acceptance criteria - Eligible hold confirms once - Expired hold cannot confirm - Cleanup cannot remove confirmed reservation Implementation constraints - Compare time inside the authoritative transition. Verification - Confirm before boundary - Race confirm with expiry cleanup Deliverables - Confirmation transition and boundary cases Rollout and recovery: Pause confirmation if atomicity fails. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CAUCT-106 — Replay workshop hold requests with the same idempotency key **Story · Medium priority · Intermediate** noCV practice brief v5 · CAUCT-106 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Resolve concurrent changes. Depends on: CAUCT-103. Difficulty: Intermediate. Estimated focused work: 135 minutes; setup and prerequisite tickets are additional. Estimated field mix: Backend 50% · Database engineering 30% · API design 20%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Timeout retry creates two holds for one user's click. Bind the operation key to the normalized request. Acceptance criteria - Same key and payload returns same hold - Different payload conflicts - Keys remain scoped to owner Implementation constraints - Store idempotency result with the hold transaction. Verification - Replay accepted request - Reuse key with different quantity Deliverables - Idempotent create contract Rollout and recovery: Require status lookup while replay support is repaired. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CAUCT-107 — Publish workshop availability changes only after commit **Bug · High priority · Expert** noCV practice brief v5 · CAUCT-107 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Resolve concurrent changes. Depends on: CAUCT-105, CAUCT-106. Difficulty: Expert. Estimated focused work: 240 minutes; setup and prerequisite tickets are additional. Estimated field mix: Distributed systems 50% · Database engineering 30% · Real-time systems 20%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Clients see seats disappear for a transaction that later rolls back. Publish committed availability through an outbox. Acceptance criteria - Committed changes enqueue events - Rollback emits no event - Replay cannot double-apply availability Implementation constraints - Event consumers receive versions, not count deltas alone. Verification - Commit hold and publish - Roll back after preparing event Deliverables - Outbox handoff and rollback cases Rollout and recovery: Stop live updates and serve authoritative snapshots. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. ### Synchronize the audience Keep availability and recovery bounded. #### CAUCT-108 — Rebuild workshop availability after a missed realtime update **Story · High priority · Advanced** noCV practice brief v5 · CAUCT-108 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Synchronize the audience. Depends on: CAUCT-107. Difficulty: Advanced. Estimated focused work: 165 minutes; setup and prerequisite tickets are additional. Estimated field mix: Real-time systems 50% · Distributed systems 50%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Dropped socket messages leave the workshop full after holds expire. Detect version gaps and refresh a snapshot. Acceptance criteria - Versions advance monotonically - Gap triggers resync - Stale events cannot reduce version Implementation constraints - Snapshot and event versions share one scope. Verification - Apply contiguous updates - Skip one version and reconnect Deliverables - Versioned client projection Rollout and recovery: Poll snapshots if delta recovery fails. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CAUCT-109 — Display workshop hold countdown as advisory **Bug · Medium priority · Intermediate** noCV practice brief v5 · CAUCT-109 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Synchronize the audience. Depends on: CAUCT-105, CAUCT-108. Difficulty: Intermediate. Estimated focused work: 105 minutes; setup and prerequisite tickets are additional. Estimated field mix: Frontend 70% · Real-time systems 30%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. A client clock skew shows time remaining after the server expired the hold. Label countdown and reconcile server refusal. Acceptance criteria - Countdown uses server offset estimate - Zero disables local confirmation - Server expiry still wins Implementation constraints - A visual timer cannot authorize a reservation. Verification - Use skewed client clock - Confirm after authoritative expiry Deliverables - Countdown presenter and skew cases Rollout and recovery: Replace countdown with expiry timestamp if offset is unreliable. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CAUCT-110 — Bound workshop hold cleanup batches and expose progress **Chore · Medium priority · Intermediate** noCV practice brief v5 · CAUCT-110 · A realtime reservation window for workshop seats Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Synchronize the audience. Depends on: CAUCT-107, CAUCT-108. Difficulty: Intermediate. Estimated focused work: 120 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 50% · Data engineering 30% · Performance engineering 20%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Cleanup scans every historical hold on each tick. Add bounded cursor batches with repeat-safe transitions. Acceptance criteria - Each batch has fixed limit - Concurrent confirms are preserved - Restart resumes without skipping eligible rows Implementation constraints - Use indexed expiry selection in the adapter design. Verification - Clean several batches - Confirm a selected hold concurrently Deliverables - Cleanup worker contract and restart cases Rollout and recovery: Pause cleanup and rely on read-time expiry until repaired. Project prerequisites: Create synthetic workshops with small capacities. Implement local transactional hold storage and injected clocks. Engineer value: Practice contention, expiry and truthful realtime projections. Company value: Inspect whether concurrent clients avoid overselling and recover uncertain results. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence.