{ "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": "44b0aa09-eac0-47a8-a450-4c9d42212ceb", "key": "CKV", "title": "A crash-consistent local key-value store", "field": "Storage systems", "summary": "Implement bounded log, index and compaction behavior in a dedicated fixture directory.", "context": "Fictional desktop cache Pebble needs a small embedded key-value engine. Build against generated keys and bytes using an ordinary filesystem adapter; no production database replacement is implied.", "stack": [ "TypeScript", "Filesystem adapter", "Vitest" ], "prerequisites": [ "Create a disposable local fixture directory.", "Implement fault injection for partial writes, sync failure and process restart." ], "developerValue": "Practice storage formats, durability boundaries and corruption handling.", "companyValue": "Inspect whether an engineer can state and test persistence guarantees.", "delivery": "Each ticket adds one narrow engine behavior; publish measured local limits, not database performance claims.", "phases": [ { "id": "records", "title": "Specify records", "goal": "Define bounded encoding and reads." }, { "id": "durability", "title": "Recover durable writes", "goal": "Handle torn records and atomic updates." }, { "id": "compaction", "title": "Reclaim old storage", "goal": "Compact safely and inspect damage." } ], "tickets": [ { "id": "daf3225e-137d-4bc7-8182-34c352037514", "key": "CKV-101", "title": "Encode local key-value records with explicit length limits", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 90, "phaseId": "records", "dependsOn": [], "scenario": "Delimiter-based records fail when values contain newlines. Add a length-prefixed binary record format.", "acceptanceCriteria": [ "Arbitrary bytes round-trip", "Key and value limits are enforced", "Version is encoded explicitly" ], "implementationNotes": [ "Specify byte order in the format note." ], "verification": [ "Round-trip binary fixture", "Reject oversized declared length" ], "deliverables": [ "Encoder decoder and format document" ], "rollout": "Keep old files read-only until conversion is explicit.", "skills": [ "Binary formats", "Validation" ], "fieldMix": [ { "field": "Storage systems", "percentage": 70 }, { "field": "Database engineering", "percentage": 30 } ], "patterns": [] }, { "id": "a01af955-b426-434f-9acc-a21d44485062", "key": "CKV-102", "title": "Distinguish missing local keys from empty values", "type": "BUG", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 60, "phaseId": "records", "dependsOn": [ "CKV-101" ], "scenario": "Empty buffers are interpreted as Not found. Return explicit presence separate from byte length.", "acceptanceCriteria": [ "Empty stored value is found", "Absent key is missing", "Deletion yields missing" ], "implementationNotes": [ "Avoid truthiness checks on encoded values." ], "verification": [ "Read empty value", "Read deleted key" ], "deliverables": [ "Read result contract and cases" ], "rollout": "Revert callers to explicit result checking.", "skills": [ "API design", "Data contracts" ], "fieldMix": [ { "field": "API design", "percentage": 60 }, { "field": "Storage systems", "percentage": 40 } ], "patterns": [] }, { "id": "3d1f87ee-1660-428b-8bd1-fd26efcc5268", "key": "CKV-103", "title": "Build a local key-value index from validated log records", "type": "TASK", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 135, "phaseId": "records", "dependsOn": [ "CKV-101", "CKV-102" ], "scenario": "Startup trusts offsets without reading record boundaries. Rebuild the index only from validated records.", "acceptanceCriteria": [ "Latest valid record wins", "Offsets stay within file bounds", "Invalid record reports its position" ], "implementationNotes": [ "Do not allocate from untrusted length fields before bounds checks." ], "verification": [ "Rebuild repeated keys", "Use record extending past EOF" ], "deliverables": [ "Startup index and malformed-file cases" ], "rollout": "Refuse writes to logs that cannot be validated.", "skills": [ "Indexing", "Parsing" ], "fieldMix": [ { "field": "Storage systems", "percentage": 60 }, { "field": "Database engineering", "percentage": 40 } ], "patterns": [] }, { "id": "cbca80da-8644-4ab4-a503-e9e38c163942", "key": "CKV-104", "title": "Declare local write acknowledgement after the durability barrier", "type": "BUG", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "durability", "dependsOn": [ "CKV-103" ], "scenario": "Put returns success before the log flush completes. Define durable acknowledgement using the filesystem adapter.", "acceptanceCriteria": [ "Success follows required sync", "Sync failure reports uncertain outcome", "Failed acknowledgement is not silently retried as new write" ], "implementationNotes": [ "Document the adapter's actual durability assumptions." ], "verification": [ "Put with successful sync", "Inject sync failure after write" ], "deliverables": [ "Acknowledgement contract and fault cases" ], "rollout": "Switch to read-only if durability barriers fail repeatedly.", "skills": [ "Durability", "Filesystem" ], "fieldMix": [ { "field": "Storage systems", "percentage": 70 }, { "field": "Database engineering", "percentage": 30 } ], "patterns": [] }, { "id": "ed92f3fc-6774-4f5a-ae3e-ccc151879c25", "key": "CKV-105", "title": "Recover a torn key-value record at the end of the log", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "durability", "dependsOn": [ "CKV-103", "CKV-104" ], "scenario": "A crash leaves a partial final record and startup refuses every key. Recover the valid prefix conservatively.", "acceptanceCriteria": [ "Valid prefix remains readable", "Incomplete tail is identified", "Middle corruption fails closed" ], "implementationNotes": [ "Tail truncation requires an explicit recovery mode." ], "verification": [ "Recover partial final record", "Corrupt middle record" ], "deliverables": [ "Tail recovery and corruption cases" ], "rollout": "Preserve original log before applying tail repair.", "skills": [ "Crash recovery", "Integrity" ], "fieldMix": [ { "field": "Storage systems", "percentage": 80 }, { "field": "Database engineering", "percentage": 20 } ], "patterns": [] }, { "id": "98c02751-686e-4111-be42-5942dbc0030b", "key": "CKV-106", "title": "Represent key deletion as an ordered tombstone", "type": "STORY", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 120, "phaseId": "durability", "dependsOn": [ "CKV-104", "CKV-105" ], "scenario": "Rebuilding the index resurrects deleted keys because deletion only changed memory. Append durable tombstones.", "acceptanceCriteria": [ "Deleted keys stay missing after restart", "Later puts can recreate key", "Tombstones obey acknowledgement rules" ], "implementationNotes": [ "Keep record ordering authoritative." ], "verification": [ "Delete and restart", "Fail tombstone sync" ], "deliverables": [ "Tombstone format and restart cases" ], "rollout": "Disable deletion if durable ordering is uncertain.", "skills": [ "Log structure", "State transitions" ], "fieldMix": [ { "field": "Storage systems", "percentage": 60 }, { "field": "Database engineering", "percentage": 40 } ], "patterns": [] }, { "id": "00b72a1b-d035-44b4-b4c0-bcce25ce1856", "key": "CKV-107", "title": "Reject key-value batches that cannot commit atomically", "type": "TASK", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 240, "phaseId": "durability", "dependsOn": [ "CKV-104", "CKV-106" ], "scenario": "A multi-key update survives restart with only half its changes. Add one bounded batch commit marker protocol.", "acceptanceCriteria": [ "Complete batch applies all records", "Uncommitted batch applies none", "Batch size is capped" ], "implementationNotes": [ "Do not claim filesystem transaction support that the adapter lacks." ], "verification": [ "Restart after committed batch", "Crash before commit marker" ], "deliverables": [ "Batch protocol and fault schedule" ], "rollout": "Disable batch writes while preserving single-key operations.", "skills": [ "Atomicity", "Storage engines" ], "fieldMix": [ { "field": "Database engineering", "percentage": 60 }, { "field": "Storage systems", "percentage": 40 } ], "patterns": [] }, { "id": "ac17014d-7abc-48aa-86ba-12316d934641", "key": "CKV-108", "title": "Compact the local log without changing visible key values", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 210, "phaseId": "compaction", "dependsOn": [ "CKV-106", "CKV-107" ], "scenario": "Repeated updates grow the log. Write a compacted generation from one consistent logical view.", "acceptanceCriteria": [ "Latest live values survive", "Deleted keys stay absent", "Compaction output validates before activation" ], "implementationNotes": [ "Bound memory by documented fixture limits or streaming plan." ], "verification": [ "Compare reads before and after", "Inject corrupted output record" ], "deliverables": [ "Compaction writer and equivalence cases" ], "rollout": "Discard unactivated compacted generation on failure.", "skills": [ "Compaction", "Data integrity" ], "fieldMix": [ { "field": "Storage systems", "percentage": 50 }, { "field": "Database engineering", "percentage": 30 }, { "field": "Performance engineering", "percentage": 20 } ], "patterns": [] }, { "id": "88cbf4e0-5570-489a-ab70-d1e8b50cd685", "key": "CKV-109", "title": "Activate a compacted key-value generation recoverably", "type": "BUG", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 240, "phaseId": "compaction", "dependsOn": [ "CKV-108" ], "scenario": "Crashing during compacted-file replacement leaves no selected log. Add a recoverable generation manifest.", "acceptanceCriteria": [ "One valid generation is selected", "Interrupted switch retains fallback", "Repeated recovery makes same choice" ], "implementationNotes": [ "Keep previous generation until activation is durable." ], "verification": [ "Crash at switch boundaries", "Remove incomplete new generation" ], "deliverables": [ "Generation activation and crash tests" ], "rollout": "Restore the last validated manifest and retain both files.", "skills": [ "Crash consistency", "Manifests" ], "fieldMix": [ { "field": "Storage systems", "percentage": 70 }, { "field": "Database engineering", "percentage": 30 } ], "patterns": [] }, { "id": "101d5111-9ef0-4e1d-b849-50e5fa7f92a8", "key": "CKV-110", "title": "Inspect local key-value corruption without modifying files", "type": "CHORE", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 120, "phaseId": "compaction", "dependsOn": [ "CKV-105", "CKV-109" ], "scenario": "Support has no way to identify damaged record offsets safely. Add a read-only inspection command.", "acceptanceCriteria": [ "Reports format and valid prefix", "Never rewrites bytes", "Output omits values by default" ], "implementationNotes": [ "Restrict command to an explicitly supplied fixture path." ], "verification": [ "Inspect healthy log", "Inspect malformed length and checksum" ], "deliverables": [ "Inspector and immutable-input checks" ], "rollout": "Remove repair suggestions if they imply automatic destructive changes.", "skills": [ "Diagnostics", "CLI" ], "fieldMix": [ { "field": "Developer tooling", "percentage": 50 }, { "field": "Storage systems", "percentage": 50 } ], "patterns": [] } ] } ] }