{ "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": "0f2b69f0-2ba0-45e4-86a1-735091cab32b", "key": "ABOOK", "title": "Repair appointment holds and cancellation windows", "field": "Backend", "summary": "Keep scarce appointment slots consistent through holds, confirmations and cancellation.", "context": "A fictional equipment service books maintenance visits. Expiring checkout holds and reschedules occasionally double-book a technician.", "stack": [ "TypeScript", "PostgreSQL", "REST" ], "prerequisites": [ "Build synthetic technicians, slots and booking records.", "Use an injectable clock and separate clients for concurrency probes." ], "developerValue": "Practice resource allocation, interval conflicts and durable workflows.", "companyValue": "Review scheduling correctness and recovery before exposing scarce capacity.", "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": "slots", "title": "Define availability", "goal": "Make time and availability rules unambiguous." }, { "id": "booking", "title": "Protect reservations", "goal": "Handle simultaneous actions and durable transitions." }, { "id": "operations", "title": "Operate the calendar", "goal": "Reconcile state and explain cancellations." } ], "tickets": [ { "id": "daa5d0cd-c14a-4ac7-97bd-c16ae291cd6e", "key": "ABOOK-101", "title": "Normalize maintenance-slot requests to explicit UTC intervals", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 75, "phaseId": "slots", "dependsOn": [], "scenario": "A technician's daylight-saving transition produces two appointments labelled 01:30 with no offset in the booking request.", "acceptanceCriteria": [ "Require start, end and explicit offset.", "Reject end-before-start and zero-duration intervals.", "Persist UTC while returning the requested display zone separately." ], "implementationNotes": [ "Create synthetic ambiguous-hour cases rather than reading real calendars." ], "verification": [ "Round-trip two different offsets for the repeated hour.", "Reject an offset-free repeated-hour request." ], "deliverables": [ "Slot input contract and DST cases" ], "rollout": "Add validation before new slot creation; retain original timestamps for existing rows.", "skills": [ "Time zones", "Validation" ], "fieldMix": [ { "field": "Backend", "percentage": 70 }, { "field": "API design", "percentage": 30 } ], "patterns": [] }, { "id": "7ef0824d-ede6-4b1d-95b1-b50ea07c57ff", "key": "ABOOK-102", "title": "Model overlapping technician availability as half-open intervals", "type": "TASK", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "slots", "dependsOn": [ "ABOOK-101" ], "scenario": "Adjacent visits are rejected as overlapping, while a visit completely containing another can pass a naive endpoint check.", "acceptanceCriteria": [ "Adjacent end and start boundaries do not conflict.", "Contained and partially overlapping intervals conflict.", "Conflict checks include the technician's organization." ], "implementationNotes": [ "Document the half-open interval convention in the query." ], "verification": [ "Check adjacent, contained and identical intervals.", "Try the same technician identifier in another organization and deny access." ], "deliverables": [ "Overlap query and interval matrix" ], "rollout": "Shadow-check overlap decisions; restore the old route if new conflicts need review.", "skills": [ "SQL", "Interval reasoning" ], "fieldMix": [ { "field": "Backend", "percentage": 50 }, { "field": "Database engineering", "percentage": 50 } ], "patterns": [] }, { "id": "5358fce8-2a7b-482f-b4f4-01853c15ba7a", "key": "ABOOK-103", "title": "Return bookable slots in stable bounded pages", "type": "STORY", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 90, "phaseId": "slots", "dependsOn": [ "ABOOK-101", "ABOOK-102" ], "scenario": "A busy service desk loads every future slot; several slots disappear from the second page when a new slot is inserted.", "acceptanceCriteria": [ "Order by start instant and opaque slot ID.", "Use a cursor bound to technician and date window.", "Enforce a maximum page size and bounded date range." ], "implementationNotes": [ "Do not expose unassigned technicians outside the organization." ], "verification": [ "Insert a slot between pages and inspect stable cursor progression.", "Reject an altered cursor scope and excessive range." ], "deliverables": [ "Availability page contract and cursor tests" ], "rollout": "Introduce cursor pagination alongside the old bounded endpoint; roll back its link.", "skills": [ "Pagination", "API contracts" ], "fieldMix": [ { "field": "API design", "percentage": 60 }, { "field": "Backend", "percentage": 40 } ], "patterns": [] }, { "id": "dce90584-399b-48ac-a05c-7174e8e4dd42", "key": "ABOOK-104", "title": "Reserve one active hold for a contested maintenance slot", "type": "STORY", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "booking", "dependsOn": [ "ABOOK-102" ], "scenario": "Two customers reach checkout together and each receives a valid hold token for the same appointment.", "acceptanceCriteria": [ "One active hold wins for a slot under concurrent requests.", "The loser gets a conflict without another customer's details.", "Hold creation and its expiry time commit atomically." ], "implementationNotes": [ "Use a database invariant as the final concurrency guard." ], "verification": [ "Start two clients at a barrier and assert one live hold.", "Force commit failure and assert no usable token escapes." ], "deliverables": [ "Hold command and concurrent reservation test" ], "rollout": "Enable holds on synthetic slots; pause new holds if invariant monitoring detects duplicates.", "skills": [ "Concurrency", "Database constraints" ], "fieldMix": [ { "field": "Database engineering", "percentage": 60 }, { "field": "Backend", "percentage": 40 } ], "patterns": [] }, { "id": "eb82de4e-1230-4e28-be4b-6257962c011f", "key": "ABOOK-105", "title": "Expire holds without cancelling a booking confirmed at the boundary", "type": "BUG", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 360, "phaseId": "booking", "dependsOn": [ "ABOOK-104" ], "scenario": "An expiry worker reads an old hold while checkout confirms it; the worker then frees a slot already sold.", "acceptanceCriteria": [ "Confirm and expire use guarded state transitions.", "Exactly one terminal outcome wins at the expiry boundary.", "A stale expiry job cannot alter a confirmed booking." ], "implementationNotes": [ "Specify whether confirmation at the exact deadline is rejected." ], "verification": [ "Race confirmation and expiry with a controlled clock.", "Retry the stale expiry after confirmation and retain the booking." ], "deliverables": [ "Hold state machine and boundary race reproduction" ], "rollout": "Canary the guarded worker; stop expiry consumption while preserving stored deadlines.", "skills": [ "State machines", "Concurrency" ], "fieldMix": [ { "field": "Backend", "percentage": 60 }, { "field": "Database engineering", "percentage": 40 } ], "patterns": [] }, { "id": "a6470b32-f390-443c-b148-1e3b7185b67b", "key": "ABOOK-106", "title": "Reschedule a visit without releasing its old slot prematurely", "type": "STORY", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "booking", "dependsOn": [ "ABOOK-104", "ABOOK-105" ], "scenario": "A reschedule releases the old appointment before reserving the new one, leaving customers unbooked if the target is taken.", "acceptanceCriteria": [ "Reserve the target and release the source atomically.", "Retain the original appointment on target conflict.", "A retried successful command returns the same replacement." ], "implementationNotes": [ "Keep both slot locks in a documented stable order." ], "verification": [ "Move a visit and inspect one confirmed appointment.", "Race for the target and verify the losing reschedule keeps its source." ], "deliverables": [ "Reschedule command and transaction tests" ], "rollout": "Enable for synthetic bookings; disable rescheduling while ordinary reads continue.", "skills": [ "Transactions", "Idempotency" ], "fieldMix": [ { "field": "Database engineering", "percentage": 60 }, { "field": "Backend", "percentage": 40 } ], "patterns": [] }, { "id": "ee2bec23-cee2-4128-bf69-84682be53eef", "key": "ABOOK-107", "title": "Calculate the cancellation window from the booked service policy", "type": "TASK", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "booking", "dependsOn": [ "ABOOK-105" ], "scenario": "A policy update changes the cancellation deadline for appointments sold under yesterday's terms.", "acceptanceCriteria": [ "Booking retains the applied policy version.", "Deadline calculation uses that frozen policy and UTC start.", "Cancellation returns the policy version and eligibility reason." ], "implementationNotes": [ "This exercise models eligibility only, without charging money." ], "verification": [ "Cancel bookings created under two policy versions.", "Change the current policy and verify old booking deadlines remain fixed." ], "deliverables": [ "Versioned cancellation calculator" ], "rollout": "Publish a new policy version for new bookings; keep historical policy references intact.", "skills": [ "Versioning", "Business rules" ], "fieldMix": [ { "field": "Backend", "percentage": 100 } ], "patterns": [] }, { "id": "83587c7d-baa7-46cf-93cd-6d0b4a361f15", "key": "ABOOK-108", "title": "Detect orphan holds without changing confirmed appointments", "type": "CHORE", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 210, "phaseId": "operations", "dependsOn": [ "ABOOK-105", "ABOOK-106" ], "scenario": "A simulated outage leaves holds whose expiry jobs were never dispatched; operations needs a bounded reconciliation command.", "acceptanceCriteria": [ "Scan expired held rows with cursor checkpoints.", "Release only rows still held at the checked version.", "Report confirmed rows skipped after concurrent change." ], "implementationNotes": [ "Use dry-run by default and limit each batch." ], "verification": [ "Reconcile an expired orphan and resume from a checkpoint.", "Confirm between scan and update and verify the booking survives." ], "deliverables": [ "Orphan-hold reconciler and race check" ], "rollout": "Dry-run a bounded window; stop reconciliation and retain checkpoints if unexpected skips grow.", "skills": [ "Reconciliation", "Optimistic concurrency" ], "fieldMix": [ { "field": "Backend", "percentage": 50 }, { "field": "Database engineering", "percentage": 30 }, { "field": "Site reliability", "percentage": 20 } ], "patterns": [] }, { "id": "6cd93527-9909-4c7a-97e6-6684a732ba98", "key": "ABOOK-109", "title": "Hide customer details in scheduling conflict responses", "type": "BUG", "priority": "HIGH", "difficulty": "FOUNDATIONAL", "estimateMinutes": 75, "phaseId": "operations", "dependsOn": [ "ABOOK-106", "ABOOK-107" ], "scenario": "A failed reschedule currently returns the target booking object, exposing the name and contact information of its owner.", "acceptanceCriteria": [ "Conflict responses contain only code and requested slot identity.", "Internal logs omit customer contact fields.", "Successful owners still receive their own booking projection." ], "implementationNotes": [ "Use explicit response schemas instead of deleting selected fields." ], "verification": [ "Check an owner's successful reschedule response.", "Force a conflict and assert another customer's fields appear nowhere in response or log." ], "deliverables": [ "Sanitized conflict schema and disclosure regression" ], "rollout": "Deploy response shaping first; revert only with the same restricted projection.", "skills": [ "Privacy", "Response schemas" ], "fieldMix": [ { "field": "Privacy engineering", "percentage": 50 }, { "field": "Backend", "percentage": 30 }, { "field": "API design", "percentage": 20 } ], "patterns": [] }, { "id": "2460e8d0-0a03-4a7a-b747-3a1e23fa1e1e", "key": "ABOOK-110", "title": "Prove booking recovery after a lost confirmation response", "type": "TASK", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 300, "phaseId": "operations", "dependsOn": [ "ABOOK-105", "ABOOK-108", "ABOOK-109" ], "scenario": "Checkout commits successfully, then the connection closes. A customer retries while the expiry worker is also running.", "acceptanceCriteria": [ "Document persisted state at each interruption point.", "A stable command key resolves the committed confirmation.", "No retry creates a second booking or frees its slot." ], "implementationNotes": [ "Build a deterministic fault-injection harness using synthetic visits." ], "verification": [ "Drop the response after commit and retry to the same booking.", "Drop before commit, run expiry, and verify the declared expired outcome." ], "deliverables": [ "Recovery trace and executable interruption probe" ], "rollout": "Run the drill before enabling checkout; fall back to read-only booking lookup during incidents.", "skills": [ "Fault injection", "Recovery" ], "fieldMix": [ { "field": "Quality engineering", "percentage": 40 }, { "field": "Backend", "percentage": 30 }, { "field": "Distributed systems", "percentage": 30 } ], "patterns": [] } ] } ] }