{ "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": "c9f3c302-8964-4275-ba34-361bc13c1d07", "key": "CDOWN", "title": "A dependable mobile course-download shelf", "field": "Mobile", "summary": "Manage resumable public-content downloads and safe local playback state.", "context": "Fictional learning app Birch offers synthetic text and small local media fixtures through a loopback adapter. No copyrighted course assets or network accounts are needed.", "stack": [ "React Native", "TypeScript", "SQLite", "Emulator" ], "prerequisites": [ "Create small local byte fixtures and a range-response stub.", "Simulate low storage, interruptions and stale manifests." ], "developerValue": "Practice mobile file lifecycles and background state recovery.", "companyValue": "Inspect predictable resource usage and truthful download status.", "delivery": "Use generated local fixtures; app-store publishing is outside scope.", "phases": [ { "id": "shelf", "title": "Describe downloads", "goal": "Model local content and sizes." }, { "id": "transfer", "title": "Handle transfer boundaries", "goal": "Verify and recover bytes." }, { "id": "lifecycle", "title": "Maintain the shelf", "goal": "Clean up and explain resource failures." } ], "tickets": [ { "id": "a5a79885-e03a-44a5-b0eb-3c45ce51e13d", "key": "CDOWN-101", "title": "Distinguish unknown course-download sizes from zero bytes", "type": "BUG", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 60, "phaseId": "shelf", "dependsOn": [], "scenario": "Unmeasured courses show 0 MB and users assume downloads are free of storage cost. Display size uncertainty.", "acceptanceCriteria": [ "Unknown size is labeled", "Zero-byte fixtures remain valid", "Unit formatting has boundary tests" ], "implementationNotes": [ "Do not invent estimates without metadata." ], "verification": [ "Render zero and unknown", "Render malformed size" ], "deliverables": [ "Size formatter and shelf states" ], "rollout": "Fall back to byte counts for known values.", "skills": [ "Formatting", "UX" ], "fieldMix": [ { "field": "Mobile", "percentage": 100 } ], "patterns": [] }, { "id": "63240b04-034f-470e-8fec-b277528a15c3", "key": "CDOWN-102", "title": "Keep mobile download buttons consistent with durable state", "type": "TASK", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 105, "phaseId": "shelf", "dependsOn": [], "scenario": "Returning to the shelf shows Download while a transfer is active. Render controls from one persisted lifecycle.", "acceptanceCriteria": [ "Active transfer shows pause", "Completed content shows open", "Invalid states do not expose start" ], "implementationNotes": [ "Define explicit lifecycle transitions." ], "verification": [ "Navigate away and return", "Load corrupt lifecycle value" ], "deliverables": [ "Download-state projection" ], "rollout": "Disable new downloads if state cannot be read.", "skills": [ "State machines", "Persistence" ], "fieldMix": [ { "field": "Mobile", "percentage": 80 }, { "field": "Storage systems", "percentage": 20 } ], "patterns": [] }, { "id": "69e55e83-3c66-4aa6-bf4a-e1a0c3399a46", "key": "CDOWN-103", "title": "Validate course manifest paths before creating files", "type": "BUG", "priority": "HIGH", "difficulty": "INTERMEDIATE", "estimateMinutes": 120, "phaseId": "shelf", "dependsOn": [ "CDOWN-101" ], "scenario": "A malformed manifest filename can escape its course directory. Restrict all destinations to a scoped cache root.", "acceptanceCriteria": [ "Traversal is rejected", "Absolute paths are rejected", "Valid nested relative paths stay scoped" ], "implementationNotes": [ "Resolve paths before opening files." ], "verification": [ "Write a valid nested fixture", "Reject parent-directory and drive paths" ], "deliverables": [ "Manifest path validator" ], "rollout": "Reject new manifests until path validation is restored.", "skills": [ "Filesystem", "Input security" ], "fieldMix": [ { "field": "Security", "percentage": 60 }, { "field": "Storage systems", "percentage": 20 }, { "field": "Mobile", "percentage": 20 } ], "patterns": [] }, { "id": "a37b82a5-3097-47a8-b6f3-9fc4251423e1", "key": "CDOWN-104", "title": "Resume a mobile course transfer only with matching content identity", "type": "STORY", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "transfer", "dependsOn": [ "CDOWN-102", "CDOWN-103" ], "scenario": "A paused transfer resumes after content changed and produces mixed bytes. Bind ranges to a manifest version.", "acceptanceCriteria": [ "Resume checks content identity", "Mismatch discards incompatible partial bytes", "Restart remains explicit in UI" ], "implementationNotes": [ "Treat ETags as opaque validators." ], "verification": [ "Resume unchanged fixture", "Change validator during pause" ], "deliverables": [ "Range-resume coordinator" ], "rollout": "Disable resume and restart from zero safely.", "skills": [ "HTTP", "Integrity" ], "fieldMix": [ { "field": "Storage systems", "percentage": 40 }, { "field": "Networking", "percentage": 30 }, { "field": "Mobile", "percentage": 30 } ], "patterns": [] }, { "id": "2cba4bfc-9ce8-4f34-8471-f5265a4e39c7", "key": "CDOWN-105", "title": "Verify downloaded course bytes before exposing Open", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "transfer", "dependsOn": [ "CDOWN-104" ], "scenario": "A truncated transfer is marked complete because the connection closed normally. Verify length and declared digest.", "acceptanceCriteria": [ "Completed means both checks pass", "Mismatch stays unavailable", "Bad partial bytes can be removed" ], "implementationNotes": [ "Digest metadata comes from the local trusted manifest." ], "verification": [ "Download valid fixture", "Truncate or flip one byte" ], "deliverables": [ "Completion verifier and corruption cases" ], "rollout": "Disable Open for unverified content.", "skills": [ "Hashing", "Data integrity" ], "fieldMix": [ { "field": "Storage systems", "percentage": 60 }, { "field": "Mobile", "percentage": 40 } ], "patterns": [] }, { "id": "9da19238-5006-42ef-b966-b70da5aee1a7", "key": "CDOWN-106", "title": "Pause mobile transfers when storage reservation fails", "type": "STORY", "priority": "HIGH", "difficulty": "INTERMEDIATE", "estimateMinutes": 135, "phaseId": "transfer", "dependsOn": [ "CDOWN-102", "CDOWN-103" ], "scenario": "A nearly full emulator accepts several downloads and fails unpredictably. Reserve a bounded budget before writing.", "acceptanceCriteria": [ "Admission accounts for active transfers", "Failure preserves existing content", "User sees required space" ], "implementationNotes": [ "Reservation estimates must state uncertainty." ], "verification": [ "Admit fitting transfer", "Start competing transfers exceeding budget" ], "deliverables": [ "Storage admission policy" ], "rollout": "Stop new transfers while preserving installed courses.", "skills": [ "Resource management", "Concurrency" ], "fieldMix": [ { "field": "Storage systems", "percentage": 50 }, { "field": "Mobile", "percentage": 30 }, { "field": "Performance engineering", "percentage": 20 } ], "patterns": [] }, { "id": "776a4e76-9081-4c57-b692-b4995ccff979", "key": "CDOWN-107", "title": "Recover a course-download rename interrupted by process death", "type": "BUG", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 240, "phaseId": "transfer", "dependsOn": [ "CDOWN-105", "CDOWN-106" ], "scenario": "A crash between verification and final rename leaves duplicate shelf entries. Introduce a recoverable promotion record.", "acceptanceCriteria": [ "Recovery identifies one installed version", "Unverified partials stay hidden", "Repeated recovery is idempotent" ], "implementationNotes": [ "Keep metadata and file promotion reconciliation explicit." ], "verification": [ "Kill at each promotion boundary", "Repeat recovery after missing temp file" ], "deliverables": [ "Promotion journal and crash cases" ], "rollout": "Disable promotion and retain recoverable temporary files.", "skills": [ "Crash consistency", "Transactions" ], "fieldMix": [ { "field": "Storage systems", "percentage": 50 }, { "field": "Mobile", "percentage": 30 }, { "field": "Database engineering", "percentage": 20 } ], "patterns": [] }, { "id": "9449c0b3-357d-4c5e-96a8-5cdaccbf927c", "key": "CDOWN-108", "title": "Remove one downloaded course without breaking shared assets", "type": "TASK", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "lifecycle", "dependsOn": [ "CDOWN-107" ], "scenario": "Deleting a course removes an image another course references. Track local references before reclaiming shared blobs.", "acceptanceCriteria": [ "Unreferenced blobs are reclaimed", "Referenced blobs remain", "Failed cleanup is retryable" ], "implementationNotes": [ "Keep references scoped to verified manifests." ], "verification": [ "Delete unique course", "Delete course with shared asset" ], "deliverables": [ "Reference-aware cleanup" ], "rollout": "Disable physical reclamation while fixing reference accounting.", "skills": [ "Reference counting", "Storage" ], "fieldMix": [ { "field": "Storage systems", "percentage": 70 }, { "field": "Mobile", "percentage": 30 } ], "patterns": [] }, { "id": "fc923325-e7c1-4576-b712-9a5456e6b24a", "key": "CDOWN-109", "title": "Show course-download progress without rendering every chunk", "type": "BUG", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 105, "phaseId": "lifecycle", "dependsOn": [ "CDOWN-104" ], "scenario": "Small network chunks trigger excessive mobile renders. Coalesce progress updates while keeping completion immediate.", "acceptanceCriteria": [ "Updates have bounded frequency", "Completion bypasses throttle", "Paused bytes remain accurate" ], "implementationNotes": [ "Use an injected scheduler." ], "verification": [ "Stream many chunks", "Pause between scheduled updates" ], "deliverables": [ "Progress coalescer and render-count check" ], "rollout": "Reduce to coarse milestones if scheduling regresses.", "skills": [ "Rendering", "Performance" ], "fieldMix": [ { "field": "Performance engineering", "percentage": 60 }, { "field": "Mobile", "percentage": 40 } ], "patterns": [] }, { "id": "df1317f2-dad1-4fd2-856b-69c2e4f0ceab", "key": "CDOWN-110", "title": "Provide a local download repair action with explicit scope", "type": "STORY", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 120, "phaseId": "lifecycle", "dependsOn": [ "CDOWN-108", "CDOWN-109" ], "scenario": "Users cannot recover one corrupt course without clearing the entire app. Add repair for the selected course only.", "acceptanceCriteria": [ "Repair revalidates selected files", "Other courses remain intact", "Offline repair explains deferred bytes" ], "implementationNotes": [ "Never clear account or unrelated application storage." ], "verification": [ "Repair corrupted fixture", "Run repair offline" ], "deliverables": [ "Scoped repair flow and isolation checks" ], "rollout": "Hide repair if deletion scope cannot be established.", "skills": [ "Recovery", "Isolation" ], "fieldMix": [ { "field": "Mobile", "percentage": 50 }, { "field": "Storage systems", "percentage": 50 } ], "patterns": [] } ] } ] }