{ "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": "257f157a-6e2f-4f0a-9322-abc658a6c403", "key": "COBJS", "title": "Resumable object uploads with verified completion", "field": "Storage systems", "summary": "Build a local multipart-upload coordinator with scoped identities and integrity checks.", "context": "Fictional document archive Fern stores synthetic byte objects. Use a local S3-compatible adapter or deterministic in-memory provider; no cloud credentials are needed.", "stack": [ "TypeScript", "S3-compatible adapter", "PostgreSQL adapter", "Vitest" ], "prerequisites": [ "Generate small deterministic byte fixtures.", "Implement local multipart provider responses including timeout and missing parts." ], "developerValue": "Practice object lifecycle, retry semantics and integrity verification.", "companyValue": "Inspect whether uploads avoid corruption, orphan cost and tenant crossover.", "delivery": "Submit bounded coordinator changes; external cloud rollout is separate.", "phases": [ { "id": "contract", "title": "Define upload ownership", "goal": "Specify keys, parts and quotas." }, { "id": "completion", "title": "Complete reliably", "goal": "Handle retries and integrity boundaries." }, { "id": "recovery", "title": "Recover abandoned work", "goal": "Reclaim resources and inspect outcomes." } ], "tickets": [ { "id": "de4d8c12-7077-4a6f-9fa2-9f5b81d695c1", "key": "COBJS-101", "title": "Normalize object names without treating them as filesystem paths", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 75, "phaseId": "contract", "dependsOn": [], "scenario": "The upload API accepts ambiguous separators and empty names. Define an opaque object-name contract.", "acceptanceCriteria": [ "Valid names retain documented characters", "Empty and oversized names fail", "Normalization collisions are rejected" ], "implementationNotes": [ "Object keys are not local file paths." ], "verification": [ "Store valid unicode name", "Reject colliding normalized names" ], "deliverables": [ "Name validator and examples" ], "rollout": "Reject new ambiguous names while keeping existing reads.", "skills": [ "Object storage", "Validation" ], "fieldMix": [ { "field": "API design", "percentage": 60 }, { "field": "Storage systems", "percentage": 40 } ], "patterns": [] }, { "id": "be4f0c13-1bc6-491e-97c7-c8bad60c351c", "key": "COBJS-102", "title": "Bind multipart upload sessions to organization and object identity", "type": "BUG", "priority": "HIGH", "difficulty": "INTERMEDIATE", "estimateMinutes": 120, "phaseId": "contract", "dependsOn": [ "COBJS-101" ], "scenario": "A session ID can currently be reused against a different object. Require its original scope on every part operation.", "acceptanceCriteria": [ "Matching owner uploads", "Foreign organization is denied", "Changed object identity is rejected" ], "implementationNotes": [ "Enforce scope in the repository/provider boundary." ], "verification": [ "Upload own part", "Reuse session against foreign object" ], "deliverables": [ "Scoped session adapter and denial cases" ], "rollout": "Pause multipart writes if scope is uncertain.", "skills": [ "Authorization", "Identity" ], "fieldMix": [ { "field": "Security", "percentage": 60 }, { "field": "Storage systems", "percentage": 40 } ], "patterns": [] }, { "id": "5b6d955f-de17-4a76-9958-2e9b81376658", "key": "COBJS-103", "title": "Reject multipart uploads exceeding declared size limits", "type": "TASK", "priority": "HIGH", "difficulty": "FOUNDATIONAL", "estimateMinutes": 75, "phaseId": "contract", "dependsOn": [ "COBJS-102" ], "scenario": "The coordinator accepts an unlimited part list. Bound declared object size and per-session part count.", "acceptanceCriteria": [ "Valid declared sizes pass", "Part count has explicit maximum", "Rejected admission creates no provider session" ], "implementationNotes": [ "Limits must be checked before remote allocation." ], "verification": [ "Admit small fixture", "Reject oversized declaration" ], "deliverables": [ "Admission policy and allocation checks" ], "rollout": "Lower admission to a documented safe cap if accounting fails.", "skills": [ "Resource limits", "Contracts" ], "fieldMix": [ { "field": "Storage systems", "percentage": 50 }, { "field": "API design", "percentage": 30 }, { "field": "Performance engineering", "percentage": 20 } ], "patterns": [] }, { "id": "949898d9-c35e-46b5-ba0b-c8f45af7ef6b", "key": "COBJS-104", "title": "Retry the same multipart part without creating contradictory receipts", "type": "BUG", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "completion", "dependsOn": [ "COBJS-102", "COBJS-103" ], "scenario": "A timeout after part acceptance leads to duplicate receipts with different checksums. Bind retries to part number and digest.", "acceptanceCriteria": [ "Same bytes return stable receipt", "Different bytes require explicit replacement", "Uncertain responses reconcile with provider state" ], "implementationNotes": [ "Provider ETag is opaque unless contract says otherwise." ], "verification": [ "Retry identical part", "Retry changed bytes under same operation" ], "deliverables": [ "Part-retry coordinator and cases" ], "rollout": "Stop retries and expose reconciliation status.", "skills": [ "Idempotency", "Integrity" ], "fieldMix": [ { "field": "Storage systems", "percentage": 50 }, { "field": "Distributed systems", "percentage": 50 } ], "patterns": [] }, { "id": "9f0fd846-0b72-4401-847f-d49c31c3e0fd", "key": "COBJS-105", "title": "Validate ordered multipart completion against acknowledged parts", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "completion", "dependsOn": [ "COBJS-104" ], "scenario": "Completion silently omits a middle part and produces a shorter object. Check the requested manifest before finalization.", "acceptanceCriteria": [ "Required part numbers are contiguous", "Receipts match acknowledged digests", "Missing parts prevent completion" ], "implementationNotes": [ "Define final-part size exception explicitly." ], "verification": [ "Complete ordered fixture", "Omit or duplicate middle part" ], "deliverables": [ "Completion validator and negative cases" ], "rollout": "Disable completion until manifest validation recovers.", "skills": [ "Validation", "Object storage" ], "fieldMix": [ { "field": "Storage systems", "percentage": 80 }, { "field": "API design", "percentage": 20 } ], "patterns": [] }, { "id": "610745e9-e43b-4e21-956c-56fe2845c5ce", "key": "COBJS-106", "title": "Verify completed object content before marking it available", "type": "STORY", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "completion", "dependsOn": [ "COBJS-105" ], "scenario": "Provider completion succeeds but the assembled bytes differ from the expected digest. Introduce a verification state.", "acceptanceCriteria": [ "Available requires digest agreement", "Mismatch quarantines the object", "Verification retries do not republish" ], "implementationNotes": [ "Use bounded streaming hashing, not full-memory buffering." ], "verification": [ "Verify matching bytes", "Flip one completed byte" ], "deliverables": [ "Post-completion verifier and corruption cases" ], "rollout": "Keep newly completed objects unavailable if verification fails.", "skills": [ "Streaming", "Hashing" ], "fieldMix": [ { "field": "Storage systems", "percentage": 80 }, { "field": "Backend", "percentage": 20 } ], "patterns": [] }, { "id": "d8a8754d-2132-4652-b5ef-7342492cda13", "key": "COBJS-107", "title": "Recover a timeout between multipart finalization and metadata commit", "type": "BUG", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 240, "phaseId": "completion", "dependsOn": [ "COBJS-105", "COBJS-106" ], "scenario": "A crash after provider completion leaves the session looking incomplete. Reconcile provider outcome without creating another object.", "acceptanceCriteria": [ "Recovery locates the finalized identity", "Metadata transition repeats safely", "Ambiguous provider state stays unresolved" ], "implementationNotes": [ "Persist the completion operation before dispatch." ], "verification": [ "Crash after finalization", "Return inconclusive provider lookup" ], "deliverables": [ "Completion journal and crash schedule" ], "rollout": "Pause automatic completion recovery and retain session metadata.", "skills": [ "Crash consistency", "Reconciliation" ], "fieldMix": [ { "field": "Storage systems", "percentage": 50 }, { "field": "Distributed systems", "percentage": 30 }, { "field": "Database engineering", "percentage": 20 } ], "patterns": [] }, { "id": "70e6f4ca-b857-490e-a52b-9e37f08ba518", "key": "COBJS-108", "title": "Abort expired multipart sessions without touching completed objects", "type": "CHORE", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 135, "phaseId": "recovery", "dependsOn": [ "COBJS-107" ], "scenario": "Abandoned sessions retain billable parts. Add expiry cleanup with a guarded session transition.", "acceptanceCriteria": [ "Only expired open sessions abort", "Completed objects remain readable", "Repeated abort is harmless" ], "implementationNotes": [ "Compare session state immediately before provider action." ], "verification": [ "Clean abandoned fixture", "Race cleanup with completion" ], "deliverables": [ "Session cleanup and race case" ], "rollout": "Disable cleanup if finalization state is uncertain.", "skills": [ "Lifecycle", "Resource management" ], "fieldMix": [ { "field": "Storage systems", "percentage": 70 }, { "field": "Site reliability", "percentage": 30 } ], "patterns": [] }, { "id": "97462569-e274-4c56-a2ad-e878f93cdbab", "key": "COBJS-109", "title": "Expose multipart upload progress from acknowledged bytes", "type": "STORY", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 105, "phaseId": "recovery", "dependsOn": [ "COBJS-104", "COBJS-108" ], "scenario": "Progress reaches 100 percent before the provider accepts the final part. Count acknowledged bytes separately from verification state.", "acceptanceCriteria": [ "Progress uses accepted parts", "Completion remains pending verification", "Retransmission does not double-count" ], "implementationNotes": [ "Do not treat socket bytes sent as durable storage." ], "verification": [ "Upload three parts", "Timeout accepted part and reconcile" ], "deliverables": [ "Progress projection and cases" ], "rollout": "Display state-only progress if byte accounting diverges.", "skills": [ "State projection", "UX" ], "fieldMix": [ { "field": "Frontend", "percentage": 50 }, { "field": "Storage systems", "percentage": 30 }, { "field": "API design", "percentage": 20 } ], "patterns": [] }, { "id": "36cd1ef9-3d4c-49e6-9cc2-5f9a57457811", "key": "COBJS-110", "title": "Export multipart failure diagnostics without signed URLs", "type": "CHORE", "priority": "LOW", "difficulty": "INTERMEDIATE", "estimateMinutes": 90, "phaseId": "recovery", "dependsOn": [ "COBJS-109" ], "scenario": "Support dumps provider receipts containing temporary access URLs. Add an allowlisted diagnostic projection.", "acceptanceCriteria": [ "Includes operation and part counts", "Omits signatures and object content", "Errors use bounded categories" ], "implementationNotes": [ "Signed URLs are bearer capabilities." ], "verification": [ "Export failed session", "Inject signed URL in provider error" ], "deliverables": [ "Diagnostic schema and redaction checks" ], "rollout": "Disable exports if bearer data appears.", "skills": [ "Logging", "Security" ], "fieldMix": [ { "field": "Security", "percentage": 50 }, { "field": "Site reliability", "percentage": 30 }, { "field": "Storage systems", "percentage": 20 } ], "patterns": [] } ] } ] }