# 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. ## ACLAIM — Make a database-backed work assignment queue correct A fictional inspection service assigns review jobs to staff. Polling clients sometimes claim the same job and a disconnected client can finish work after reassignment. **Field:** Database engineering. **Suggested stack:** PostgreSQL, TypeScript. **Engineer value:** Practice database concurrency, leases and transactional invariants. **Company value:** Review whether assignment authority remains reliable during contention and recovery. **Delivery agreement:** Ten scoped tickets across three phases. Build a synthetic local service or select a ticket after recreating its prerequisites; estimates exclude setup. ### Setup prerequisites - Create synthetic jobs and two independent database clients. - Use explicit state methods and an injected clock. ### Define assignment invariants Represent queue order, ownership and deadlines. #### ACLAIM-101 — Define assignment states and their required database fields **Task · Medium priority · Foundational** noCV practice brief v5 · ACLAIM-101 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define assignment invariants. Depends on: No preceding ticket. Difficulty: Foundational. Estimated focused work: 90 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 80% · Backend 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. Rows marked assigned sometimes have no assignee or lease deadline, making recovery ambiguous. Acceptance criteria - Specify pending, assigned and terminal field invariants. - Add checks that reject contradictory state combinations. - Keep completion metadata distinct from lease metadata. Implementation constraints - Use migration-backed constraints where practical. Verification - Insert each valid synthetic state. - Attempt assigned without an assignee or deadline and verify rejection. Deliverables - Assignment schema and constraint matrix Rollout and recovery: Apply constraints after inspecting synthetic legacy rows; quarantine invalid states before enabling writes. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. #### ACLAIM-102 — Order eligible jobs with a stable tie break **Task · Medium priority · Foundational** noCV practice brief v5 · ACLAIM-102 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define assignment invariants. Depends on: ACLAIM-101. Difficulty: Foundational. Estimated focused work: 75 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 80% · Backend 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. Jobs created at the same instant appear in a different order on each poll, making starvation difficult to reproduce. Acceptance criteria - Order by declared priority, ready time and opaque job ID. - Exclude future and terminal jobs explicitly. - Bound claim candidate count. Implementation constraints - Document whether priority changes preserve or reset waiting time. Verification - Create equal-time jobs and observe stable order. - Include future and completed jobs and verify they are ineligible. Deliverables - Eligibility query and ordering fixtures Rollout and recovery: Introduce the query in read-only inspection first; restore previous routing on semantic mismatch. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. #### ACLAIM-103 — Scope work assignment queries to the operator's organization **Bug · High priority · Intermediate** noCV practice brief v5 · ACLAIM-103 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define assignment invariants. Depends on: ACLAIM-101, ACLAIM-102. Difficulty: Intermediate. Estimated focused work: 150 minutes; setup and prerequisite tickets are additional. Estimated field mix: Security 50% · Database engineering 30% · Backend 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. The job list is scoped in the controller, but the claim repository accepts a globally valid job ID. Acceptance criteria - Require organization scope at repository entry. - Claim and detail queries enforce that scope. - Return no other-organization job metadata on denial. Implementation constraints - Test direct repository calls as well as API routes. Verification - Claim a permitted synthetic job. - Claim another organization's ID and verify unchanged row state. Deliverables - Tenant-scoped assignment repository Rollout and recovery: Deploy repository guards before broader polling; inspect safe denial counters. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. ### Protect concurrent transitions Claim, renew and finish with durable authority. #### ACLAIM-104 — Claim one pending job atomically under competing pollers **Story · High priority · Advanced** noCV practice brief v5 · ACLAIM-104 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Protect concurrent transitions. Depends on: ACLAIM-102, ACLAIM-103. Difficulty: Advanced. Estimated focused work: 240 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 100%. 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 polling clients select the same pending job before either writes its assignment. Acceptance criteria - Select and transition a job within one transaction. - Use a database locking strategy with documented contention behavior. - Return distinct jobs or no work under concurrent pollers. Implementation constraints - Evaluate SKIP LOCKED against the declared ordering and fairness policy. Verification - Start two clients at a barrier and assert unique claimed identities. - Hold one candidate lock and verify the documented skip or wait behavior. Deliverables - Atomic claim query and concurrency test Rollout and recovery: Canary with two synthetic pollers; reduce concurrency if lock behavior violates the contract. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. #### ACLAIM-105 — Issue a monotonically increasing assignment generation on every reclaim **Task · Medium priority · Advanced** noCV practice brief v5 · ACLAIM-105 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Protect concurrent transitions. Depends on: ACLAIM-104. Difficulty: Advanced. Estimated focused work: 210 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 60% · Distributed systems 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. A disconnected reviewer reconnects after its job was reassigned and still holds a token that appears current. Acceptance criteria - Every new assignment increments a durable generation. - Mutation commands require job, assignee and generation. - A stale generation cannot renew or finish work. Implementation constraints - Treat the generation as authority, not a UI-only counter. Verification - Reclaim a job and complete using the new generation. - Try completion from the previous generation and reject it. Deliverables - Assignment-generation guard Rollout and recovery: Enable guarded writes before automated reclaim; retain old assignment history. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. #### ACLAIM-106 — Renew assignment leases without extending a completed job **Bug · Medium priority · Intermediate** noCV practice brief v5 · ACLAIM-106 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Protect concurrent transitions. Depends on: ACLAIM-104, ACLAIM-105. Difficulty: Intermediate. Estimated focused work: 150 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 60% · Distributed systems 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. A late heartbeat runs after completion and changes the row back into an apparently active assignment. Acceptance criteria - Renew only the current assigned generation. - Never modify terminal completion fields. - Bound extension duration using the server's clock. Implementation constraints - Use one guarded update rather than read-then-write status changes. Verification - Renew a valid active assignment. - Complete first, then send a delayed renewal and preserve terminal state. Deliverables - Lease renewal command and stale-heartbeat test Rollout and recovery: Canary renewal with short synthetic leases; pause renewal on unexpected transition conflicts. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. #### ACLAIM-107 — Finish a job and publish its result reference in one transaction **Story · Medium priority · Expert** noCV practice brief v5 · ACLAIM-107 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Protect concurrent transitions. Depends on: ACLAIM-105, ACLAIM-106. Difficulty: Expert. Estimated focused work: 300 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 80% · Backend 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 result is visible while its job remains assigned because completion and result linking commit separately. Acceptance criteria - Check assignment authority and lease at commit. - Commit terminal state and result reference atomically. - Duplicate identical completion returns the original outcome. Implementation constraints - Keep result bytes outside the database transaction; link only verified immutable identity. Verification - Complete a valid assignment with one result reference. - Force transaction failure and verify neither completion nor result publication persists. Deliverables - Completion transaction and rollback tests Rollout and recovery: Enable completion on synthetic jobs; suspend writes if authority or result verification is unavailable. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. ### Recover stale work Inspect contention and repair expired assignments. #### ACLAIM-108 — Reclaim expired assignments using current row authority **Task · Medium priority · Advanced** noCV practice brief v5 · ACLAIM-108 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Recover stale work. Depends on: ACLAIM-105, ACLAIM-106, ACLAIM-107. Difficulty: Advanced. Estimated focused work: 210 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 70% · Distributed 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 sweep selects expired jobs, then reclaims one that was renewed before its update executes. Acceptance criteria - Recheck generation, assigned state and expiry in the reclaim update. - Record previous ownership as immutable history. - Bound each sweep and expose skipped renewals. Implementation constraints - Use a controlled clock and barrier for the renewal race. Verification - Reclaim a truly expired assignment. - Renew between scan and update and verify reclaim skips it. Deliverables - Expiry reclaimer and race regression Rollout and recovery: Dry-run selected rows first; pause sweeps when clock or ownership checks disagree. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. #### ACLAIM-109 — Measure assignment lock behavior without claiming a throughput guarantee **Chore · Medium priority · Intermediate** noCV practice brief v5 · ACLAIM-109 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Recover stale work. Depends on: ACLAIM-104, ACLAIM-108. Difficulty: Intermediate. Estimated focused work: 180 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 50% · Performance engineering 30% · Quality 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. Operators need to choose a polling interval and concurrency limit based on observed contention in the local prototype. Acceptance criteria - Record database/runtime versions and synthetic job count. - Measure lock waits and claim outcomes at fixed concurrency levels. - Keep correctness assertions enabled during every run. Implementation constraints - Repeat each local condition three times; results describe only that environment. Verification - Run identical workloads at one and four pollers and record observations. - Hold a long transaction and verify timeouts remain bounded without duplicate claims. Deliverables - Contention probe and observation report Rollout and recovery: Use observations to propose conservative local limits; restore lower concurrency if claim failures rise. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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. #### ACLAIM-110 — Rehearse recovery of a queue with mixed expired and terminal jobs **Task · Medium priority · Expert** noCV practice brief v5 · ACLAIM-110 · Make a database-backed work assignment queue correct Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Recover stale work. Depends on: ACLAIM-107, ACLAIM-108, ACLAIM-109. Difficulty: Expert. Estimated focused work: 300 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 60% · Site reliability 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. After an outage, operators need to resume assignments without redoing completed work or accepting stale reviewer results. Acceptance criteria - Classify terminal, live and expired assignments from durable fields. - Reclaim only expired authority and preserve terminal results. - Report inconsistent rows instead of silently normalizing them. Implementation constraints - Use a fabricated outage dataset with one contradictory row. Verification - Recover valid mixed states and finish one reclaimed job. - Submit a stale completion and inspect the contradictory row report. Deliverables - Queue recovery runbook and executable drill Rollout and recovery: Run the drill before increasing concurrency; keep uncertain jobs quarantined for review. Project prerequisites: Create synthetic jobs and two independent database clients. Use explicit state methods and an injected clock. Engineer value: Practice database concurrency, leases and transactional invariants. Company value: Review whether assignment authority remains reliable during contention and recovery. 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.