{ "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": "870ca293-ba3d-4340-bd71-a2142fa7bef0", "key": "CAUCT", "title": "A realtime reservation window for workshop seats", "field": "Real-time systems", "summary": "Coordinate expiring seat holds and live availability in a local simulation.", "context": "Fictional craft studio Maple offers workshop seats. Implement synthetic reservations without payments or real booking services.", "stack": [ "TypeScript", "PostgreSQL adapter", "WebSocket", "Vitest" ], "prerequisites": [ "Create synthetic workshops with small capacities.", "Implement local transactional hold storage and injected clocks." ], "developerValue": "Practice contention, expiry and truthful realtime projections.", "companyValue": "Inspect whether concurrent clients avoid overselling and recover uncertain results.", "delivery": "Booking simulation only; payment and production capacity planning are excluded.", "phases": [ { "id": "holds", "title": "Define hold rules", "goal": "Specify capacity and ownership." }, { "id": "races", "title": "Resolve concurrent changes", "goal": "Handle expiry and confirmation atomically." }, { "id": "clients", "title": "Synchronize the audience", "goal": "Keep availability and recovery bounded." } ], "tickets": [ { "id": "b1149a73-eb98-44ba-a263-3ca1538e972b", "key": "CAUCT-101", "title": "Specify workshop seat counts without negative availability", "type": "TASK", "priority": "HIGH", "difficulty": "FOUNDATIONAL", "estimateMinutes": 75, "phaseId": "holds", "dependsOn": [], "scenario": "The prototype subtracts all historical holds and displays negative seats. Project availability from current authoritative states.", "acceptanceCriteria": [ "Only active holds consume seats", "Confirmed reservations consume seats", "Expired holds do not consume seats" ], "implementationNotes": [ "Define active using injected time." ], "verification": [ "Project mixed states", "Use boundary expiry instant" ], "deliverables": [ "Availability projection and cases" ], "rollout": "Hide counts if state cannot be reconciled.", "skills": [ "State modeling", "Time" ], "fieldMix": [ { "field": "Backend", "percentage": 60 }, { "field": "Database engineering", "percentage": 40 } ], "patterns": [] }, { "id": "5c7cf0d8-af2c-4eaa-8915-225612f3ce5b", "key": "CAUCT-102", "title": "Validate workshop hold quantities before storage", "type": "BUG", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 60, "phaseId": "holds", "dependsOn": [ "CAUCT-101" ], "scenario": "A zero-seat request creates a hold and a fractional request breaks counts. Enforce bounded integer quantities.", "acceptanceCriteria": [ "Positive integers within limit pass", "Zero and fractions fail", "Invalid input creates no record" ], "implementationNotes": [ "Keep limits explicit in the local contract." ], "verification": [ "Hold two seats", "Reject zero and oversized quantities" ], "deliverables": [ "Quantity validator and failure cases" ], "rollout": "Reject new holds if validation is unavailable.", "skills": [ "Validation", "Contracts" ], "fieldMix": [ { "field": "Backend", "percentage": 80 }, { "field": "API design", "percentage": 20 } ], "patterns": [] }, { "id": "86d754d4-7ef2-4eea-a645-f914809b8b5d", "key": "CAUCT-103", "title": "Create workshop holds atomically under contention", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "holds", "dependsOn": [ "CAUCT-101", "CAUCT-102" ], "scenario": "Two clients see one available seat and both reserve it. Serialize capacity consumption at storage.", "acceptanceCriteria": [ "At most capacity is consumed", "Loser receives unavailable result", "No partial hold record remains" ], "implementationNotes": [ "A browser availability check is advisory only." ], "verification": [ "Create uncontested hold", "Race two requests for one seat" ], "deliverables": [ "Transactional hold operation" ], "rollout": "Pause hold creation if capacity invariant fails.", "skills": [ "Transactions", "Concurrency" ], "fieldMix": [ { "field": "Database engineering", "percentage": 70 }, { "field": "Backend", "percentage": 30 } ], "patterns": [] }, { "id": "04228c7d-6f7b-4246-8630-6979c6c1cd30", "key": "CAUCT-104", "title": "Scope workshop hold lookup and cancellation to its owner", "type": "BUG", "priority": "HIGH", "difficulty": "INTERMEDIATE", "estimateMinutes": 135, "phaseId": "races", "dependsOn": [ "CAUCT-103" ], "scenario": "Knowing a hold ID lets another user cancel it. Enforce owner scope in the repository boundary.", "acceptanceCriteria": [ "Owner reads and cancels", "Foreign owner is denied", "Denied calls do not disclose hold details" ], "implementationNotes": [ "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": "Disable cancellation if scope cannot be established.", "skills": [ "Authorization", "Repository design" ], "fieldMix": [ { "field": "Security", "percentage": 70 }, { "field": "Backend", "percentage": 30 } ], "patterns": [] }, { "id": "be81a3d4-386e-445e-950b-0e26a2a2ee60", "key": "CAUCT-105", "title": "Confirm workshop holds only before the expiry boundary", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "races", "dependsOn": [ "CAUCT-103", "CAUCT-104" ], "scenario": "Confirm and expiry cleanup race, creating reservations from expired holds. Add an atomic transition with one time rule.", "acceptanceCriteria": [ "Eligible hold confirms once", "Expired hold cannot confirm", "Cleanup cannot remove confirmed reservation" ], "implementationNotes": [ "Compare time inside the authoritative transition." ], "verification": [ "Confirm before boundary", "Race confirm with expiry cleanup" ], "deliverables": [ "Confirmation transition and boundary cases" ], "rollout": "Pause confirmation if atomicity fails.", "skills": [ "State machines", "Concurrency" ], "fieldMix": [ { "field": "Database engineering", "percentage": 60 }, { "field": "Backend", "percentage": 40 } ], "patterns": [] }, { "id": "6fb50879-6487-4422-b12f-8ab0c1a538db", "key": "CAUCT-106", "title": "Replay workshop hold requests with the same idempotency key", "type": "STORY", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 135, "phaseId": "races", "dependsOn": [ "CAUCT-103" ], "scenario": "Timeout retry creates two holds for one user's click. Bind the operation key to the normalized request.", "acceptanceCriteria": [ "Same key and payload returns same hold", "Different payload conflicts", "Keys remain scoped to owner" ], "implementationNotes": [ "Store idempotency result with the hold transaction." ], "verification": [ "Replay accepted request", "Reuse key with different quantity" ], "deliverables": [ "Idempotent create contract" ], "rollout": "Require status lookup while replay support is repaired.", "skills": [ "Idempotency", "Transactions" ], "fieldMix": [ { "field": "Backend", "percentage": 50 }, { "field": "Database engineering", "percentage": 30 }, { "field": "API design", "percentage": 20 } ], "patterns": [] }, { "id": "d3454de1-e672-4eaa-8951-c006128c645f", "key": "CAUCT-107", "title": "Publish workshop availability changes only after commit", "type": "BUG", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 240, "phaseId": "races", "dependsOn": [ "CAUCT-105", "CAUCT-106" ], "scenario": "Clients see seats disappear for a transaction that later rolls back. Publish committed availability through an outbox.", "acceptanceCriteria": [ "Committed changes enqueue events", "Rollback emits no event", "Replay cannot double-apply availability" ], "implementationNotes": [ "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": "Stop live updates and serve authoritative snapshots.", "skills": [ "Outbox", "Consistency" ], "fieldMix": [ { "field": "Distributed systems", "percentage": 50 }, { "field": "Database engineering", "percentage": 30 }, { "field": "Real-time systems", "percentage": 20 } ], "patterns": [] }, { "id": "4fa4cebe-37e4-45e1-b75c-80ffb9380777", "key": "CAUCT-108", "title": "Rebuild workshop availability after a missed realtime update", "type": "STORY", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 165, "phaseId": "clients", "dependsOn": [ "CAUCT-107" ], "scenario": "Dropped socket messages leave the workshop full after holds expire. Detect version gaps and refresh a snapshot.", "acceptanceCriteria": [ "Versions advance monotonically", "Gap triggers resync", "Stale events cannot reduce version" ], "implementationNotes": [ "Snapshot and event versions share one scope." ], "verification": [ "Apply contiguous updates", "Skip one version and reconnect" ], "deliverables": [ "Versioned client projection" ], "rollout": "Poll snapshots if delta recovery fails.", "skills": [ "Synchronization", "Recovery" ], "fieldMix": [ { "field": "Real-time systems", "percentage": 50 }, { "field": "Distributed systems", "percentage": 50 } ], "patterns": [] }, { "id": "82e6520e-b5f2-426e-b94c-6ca80d5a55d4", "key": "CAUCT-109", "title": "Display workshop hold countdown as advisory", "type": "BUG", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 105, "phaseId": "clients", "dependsOn": [ "CAUCT-105", "CAUCT-108" ], "scenario": "A client clock skew shows time remaining after the server expired the hold. Label countdown and reconcile server refusal.", "acceptanceCriteria": [ "Countdown uses server offset estimate", "Zero disables local confirmation", "Server expiry still wins" ], "implementationNotes": [ "A visual timer cannot authorize a reservation." ], "verification": [ "Use skewed client clock", "Confirm after authoritative expiry" ], "deliverables": [ "Countdown presenter and skew cases" ], "rollout": "Replace countdown with expiry timestamp if offset is unreliable.", "skills": [ "Time", "UX" ], "fieldMix": [ { "field": "Frontend", "percentage": 70 }, { "field": "Real-time systems", "percentage": 30 } ], "patterns": [] }, { "id": "9eae6e01-e892-4f2f-98c9-0e2e84ef97d4", "key": "CAUCT-110", "title": "Bound workshop hold cleanup batches and expose progress", "type": "CHORE", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 120, "phaseId": "clients", "dependsOn": [ "CAUCT-107", "CAUCT-108" ], "scenario": "Cleanup scans every historical hold on each tick. Add bounded cursor batches with repeat-safe transitions.", "acceptanceCriteria": [ "Each batch has fixed limit", "Concurrent confirms are preserved", "Restart resumes without skipping eligible rows" ], "implementationNotes": [ "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": "Pause cleanup and rely on read-time expiry until repaired.", "skills": [ "Batch processing", "Recovery" ], "fieldMix": [ { "field": "Database engineering", "percentage": 50 }, { "field": "Data engineering", "percentage": 30 }, { "field": "Performance engineering", "percentage": 20 } ], "patterns": [] } ] } ] }