{ "policy": { "version": 5, "patterns": { "version": 1, "method": "CURATED_PRACTICE_TOPIC", "notice": "Pattern topics identify design choices to practice. Read the ticket's acceptance criteria and justify the simplest suitable approach. Tags are not capability or ownership evidence; an untagged ticket has no curated pattern topic assigned." }, "fieldMix": { "version": 1, "method": "CURATED_ESTIMATE", "notice": "Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence." }, "contentStatus": "PRACTICE_BRIEF", "assessmentStatus": "NOT_QUALIFIED", "evidenceUse": "NONE", "aiPolicy": "AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior.", "notice": "Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included.", "outcomeEvidence": "Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.", "ownershipEvidence": "Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence." }, "patternTopics": [ { "id": "factory-method", "label": "Factory Method", "group": "Creational" }, { "id": "abstract-factory", "label": "Abstract Factory", "group": "Creational" }, { "id": "builder", "label": "Builder", "group": "Creational" }, { "id": "prototype", "label": "Prototype", "group": "Creational" }, { "id": "singleton", "label": "Singleton", "group": "Creational" }, { "id": "adapter", "label": "Adapter", "group": "Structural" }, { "id": "bridge", "label": "Bridge", "group": "Structural" }, { "id": "composite", "label": "Composite", "group": "Structural" }, { "id": "decorator", "label": "Decorator", "group": "Structural" }, { "id": "facade", "label": "Facade", "group": "Structural" }, { "id": "flyweight", "label": "Flyweight", "group": "Structural" }, { "id": "proxy", "label": "Proxy", "group": "Structural" }, { "id": "chain-of-responsibility", "label": "Chain of Responsibility", "group": "Behavioral" }, { "id": "command", "label": "Command", "group": "Behavioral" }, { "id": "interpreter", "label": "Interpreter", "group": "Behavioral" }, { "id": "iterator", "label": "Iterator", "group": "Behavioral" }, { "id": "mediator", "label": "Mediator", "group": "Behavioral" }, { "id": "memento", "label": "Memento", "group": "Behavioral" }, { "id": "observer", "label": "Observer", "group": "Behavioral" }, { "id": "state", "label": "State", "group": "Behavioral" }, { "id": "strategy", "label": "Strategy", "group": "Behavioral" }, { "id": "template-method", "label": "Template Method", "group": "Behavioral" }, { "id": "visitor", "label": "Visitor", "group": "Behavioral" }, { "id": "ports-and-adapters", "label": "Ports and Adapters", "group": "Architectural" }, { "id": "cqrs", "label": "CQRS", "group": "Architectural" }, { "id": "strangler-fig", "label": "Strangler Fig", "group": "Architectural" }, { "id": "saga", "label": "Saga", "group": "Distributed and reliability" }, { "id": "transactional-outbox", "label": "Transactional Outbox", "group": "Distributed and reliability" }, { "id": "circuit-breaker", "label": "Circuit Breaker", "group": "Distributed and reliability" }, { "id": "bulkhead", "label": "Bulkhead", "group": "Distributed and reliability" } ], "projects": [ { "id": "e8d4d766-7d14-42f3-a64d-e082f72919f3", "key": "ACLAIM", "title": "Make a database-backed work assignment queue correct", "field": "Database engineering", "summary": "Claim, renew and finish work without duplicate authority or stranded assignments.", "context": "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.", "stack": [ "PostgreSQL", "TypeScript" ], "prerequisites": [ "Create synthetic jobs and two independent database clients.", "Use explicit state methods and an injected clock." ], "developerValue": "Practice database concurrency, leases and transactional invariants.", "companyValue": "Review whether assignment authority remains reliable during contention and recovery.", "delivery": "Ten scoped tickets across three phases. Build a synthetic local service or select a ticket after recreating its prerequisites; estimates exclude setup.", "phases": [ { "id": "model", "title": "Define assignment invariants", "goal": "Represent queue order, ownership and deadlines." }, { "id": "claim", "title": "Protect concurrent transitions", "goal": "Claim, renew and finish with durable authority." }, { "id": "recover", "title": "Recover stale work", "goal": "Inspect contention and repair expired assignments." } ], "tickets": [ { "id": "3fdfabc0-ac34-411a-8ead-76434d07a940", "key": "ACLAIM-101", "title": "Define assignment states and their required database fields", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 90, "phaseId": "model", "dependsOn": [], "scenario": "Rows marked assigned sometimes have no assignee or lease deadline, making recovery ambiguous.", "acceptanceCriteria": [ "Specify pending, assigned and terminal field invariants.", "Add checks that reject contradictory state combinations.", "Keep completion metadata distinct from lease metadata." ], "implementationNotes": [ "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": "Apply constraints after inspecting synthetic legacy rows; quarantine invalid states before enabling writes.", "skills": [ "Data modeling", "Check constraints" ], "fieldMix": [ { "field": "Database engineering", "percentage": 80 }, { "field": "Backend", "percentage": 20 } ], "patterns": [] }, { "id": "704313f1-6190-4f2a-bad7-d310e9a36f98", "key": "ACLAIM-102", "title": "Order eligible jobs with a stable tie break", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 75, "phaseId": "model", "dependsOn": [ "ACLAIM-101" ], "scenario": "Jobs created at the same instant appear in a different order on each poll, making starvation difficult to reproduce.", "acceptanceCriteria": [ "Order by declared priority, ready time and opaque job ID.", "Exclude future and terminal jobs explicitly.", "Bound claim candidate count." ], "implementationNotes": [ "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": "Introduce the query in read-only inspection first; restore previous routing on semantic mismatch.", "skills": [ "SQL ordering", "Queue semantics" ], "fieldMix": [ { "field": "Database engineering", "percentage": 80 }, { "field": "Backend", "percentage": 20 } ], "patterns": [] }, { "id": "77ecfee2-4d60-445e-a219-96537d7e030c", "key": "ACLAIM-103", "title": "Scope work assignment queries to the operator's organization", "type": "BUG", "priority": "HIGH", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "model", "dependsOn": [ "ACLAIM-101", "ACLAIM-102" ], "scenario": "The job list is scoped in the controller, but the claim repository accepts a globally valid job ID.", "acceptanceCriteria": [ "Require organization scope at repository entry.", "Claim and detail queries enforce that scope.", "Return no other-organization job metadata on denial." ], "implementationNotes": [ "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": "Deploy repository guards before broader polling; inspect safe denial counters.", "skills": [ "Tenant isolation", "Repository design" ], "fieldMix": [ { "field": "Security", "percentage": 50 }, { "field": "Database engineering", "percentage": 30 }, { "field": "Backend", "percentage": 20 } ], "patterns": [] }, { "id": "3bb8c64d-f79d-4857-b0c8-4bb2d8afbcf6", "key": "ACLAIM-104", "title": "Claim one pending job atomically under competing pollers", "type": "STORY", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "claim", "dependsOn": [ "ACLAIM-102", "ACLAIM-103" ], "scenario": "Two polling clients select the same pending job before either writes its assignment.", "acceptanceCriteria": [ "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." ], "implementationNotes": [ "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": "Canary with two synthetic pollers; reduce concurrency if lock behavior violates the contract.", "skills": [ "Row locking", "Transactions" ], "fieldMix": [ { "field": "Database engineering", "percentage": 100 } ], "patterns": [] }, { "id": "e33cbcfb-a0b1-47c3-a559-cfbd23e17a4b", "key": "ACLAIM-105", "title": "Issue a monotonically increasing assignment generation on every reclaim", "type": "TASK", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 210, "phaseId": "claim", "dependsOn": [ "ACLAIM-104" ], "scenario": "A disconnected reviewer reconnects after its job was reassigned and still holds a token that appears current.", "acceptanceCriteria": [ "Every new assignment increments a durable generation.", "Mutation commands require job, assignee and generation.", "A stale generation cannot renew or finish work." ], "implementationNotes": [ "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": "Enable guarded writes before automated reclaim; retain old assignment history.", "skills": [ "Fencing", "Optimistic concurrency" ], "fieldMix": [ { "field": "Database engineering", "percentage": 60 }, { "field": "Distributed systems", "percentage": 40 } ], "patterns": [] }, { "id": "f0d3bed7-ee11-45b6-95b6-450478e4848d", "key": "ACLAIM-106", "title": "Renew assignment leases without extending a completed job", "type": "BUG", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "claim", "dependsOn": [ "ACLAIM-104", "ACLAIM-105" ], "scenario": "A late heartbeat runs after completion and changes the row back into an apparently active assignment.", "acceptanceCriteria": [ "Renew only the current assigned generation.", "Never modify terminal completion fields.", "Bound extension duration using the server's clock." ], "implementationNotes": [ "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": "Canary renewal with short synthetic leases; pause renewal on unexpected transition conflicts.", "skills": [ "Guarded updates", "Lease semantics" ], "fieldMix": [ { "field": "Database engineering", "percentage": 60 }, { "field": "Distributed systems", "percentage": 40 } ], "patterns": [] }, { "id": "c7918dc1-bca9-4a84-9c19-c3df31ba0a27", "key": "ACLAIM-107", "title": "Finish a job and publish its result reference in one transaction", "type": "STORY", "priority": "MEDIUM", "difficulty": "EXPERT", "estimateMinutes": 300, "phaseId": "claim", "dependsOn": [ "ACLAIM-105", "ACLAIM-106" ], "scenario": "A result is visible while its job remains assigned because completion and result linking commit separately.", "acceptanceCriteria": [ "Check assignment authority and lease at commit.", "Commit terminal state and result reference atomically.", "Duplicate identical completion returns the original outcome." ], "implementationNotes": [ "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": "Enable completion on synthetic jobs; suspend writes if authority or result verification is unavailable.", "skills": [ "Transactions", "Result integrity" ], "fieldMix": [ { "field": "Database engineering", "percentage": 80 }, { "field": "Backend", "percentage": 20 } ], "patterns": [] }, { "id": "c83603c3-ca94-44c8-8148-b83ebb148a1f", "key": "ACLAIM-108", "title": "Reclaim expired assignments using current row authority", "type": "TASK", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 210, "phaseId": "recover", "dependsOn": [ "ACLAIM-105", "ACLAIM-106", "ACLAIM-107" ], "scenario": "A sweep selects expired jobs, then reclaims one that was renewed before its update executes.", "acceptanceCriteria": [ "Recheck generation, assigned state and expiry in the reclaim update.", "Record previous ownership as immutable history.", "Bound each sweep and expose skipped renewals." ], "implementationNotes": [ "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": "Dry-run selected rows first; pause sweeps when clock or ownership checks disagree.", "skills": [ "Concurrency", "Recovery" ], "fieldMix": [ { "field": "Database engineering", "percentage": 70 }, { "field": "Distributed systems", "percentage": 30 } ], "patterns": [] }, { "id": "b876e3a6-6868-445d-a485-7abebd6a5e0d", "key": "ACLAIM-109", "title": "Measure assignment lock behavior without claiming a throughput guarantee", "type": "CHORE", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 180, "phaseId": "recover", "dependsOn": [ "ACLAIM-104", "ACLAIM-108" ], "scenario": "Operators need to choose a polling interval and concurrency limit based on observed contention in the local prototype.", "acceptanceCriteria": [ "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." ], "implementationNotes": [ "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": "Use observations to propose conservative local limits; restore lower concurrency if claim failures rise.", "skills": [ "Database observability", "Concurrency testing" ], "fieldMix": [ { "field": "Database engineering", "percentage": 50 }, { "field": "Performance engineering", "percentage": 30 }, { "field": "Quality engineering", "percentage": 20 } ], "patterns": [] }, { "id": "8dbbb2d8-bdfa-4774-ab18-443677a49385", "key": "ACLAIM-110", "title": "Rehearse recovery of a queue with mixed expired and terminal jobs", "type": "TASK", "priority": "MEDIUM", "difficulty": "EXPERT", "estimateMinutes": 300, "phaseId": "recover", "dependsOn": [ "ACLAIM-107", "ACLAIM-108", "ACLAIM-109" ], "scenario": "After an outage, operators need to resume assignments without redoing completed work or accepting stale reviewer results.", "acceptanceCriteria": [ "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." ], "implementationNotes": [ "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": "Run the drill before increasing concurrency; keep uncertain jobs quarantined for review.", "skills": [ "Recovery", "Data integrity" ], "fieldMix": [ { "field": "Database engineering", "percentage": 60 }, { "field": "Site reliability", "percentage": 40 } ], "patterns": [] } ] } ] }