{ "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": "aeceae5d-eb1e-42b5-a19f-ba251320a8ba", "key": "BDNS", "title": "Service DNS migration lab", "field": "Networking", "summary": "Move a service endpoint while accounting for caches, negative answers, and resolver behavior.", "context": "A fictional internal API is moving to a new endpoint. The team assumes DNS changes are immediate and has no rehearsal for stale clients.", "stack": [ "TypeScript", "DNS fixtures", "HTTP" ], "prerequisites": [ "Create a local resolver simulator and two loopback service endpoints with synthetic DNS records; query no external infrastructure." ], "developerValue": "Practice DNS semantics, migration timing, and network diagnosis.", "companyValue": "Produce a migration plan that makes cache delay and endpoint compatibility explicit.", "delivery": "Deliver local DNS simulations and a cutover report; modify no real DNS records.", "phases": [ { "id": "records", "title": "Model DNS responses", "goal": "Define record and cache semantics." }, { "id": "migrate", "title": "Rehearse endpoint changes", "goal": "Handle stale clients and lookup failures." }, { "id": "assess", "title": "Review cutover", "goal": "Choose timing and recovery controls." } ], "tickets": [ { "id": "249e22a3-59c1-4588-a50e-8f5e583464b8", "key": "BDNS-101", "title": "Inventory service records and their consumers", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 60, "phaseId": "records", "dependsOn": [], "scenario": "The team knows the main hostname but not aliases used by background jobs.", "acceptanceCriteria": [ "List record types, aliases, and modeled consumers.", "Identify ownership and current TTL.", "Mark unknown client caching behavior." ], "implementationNotes": [ "Use reserved local test names only." ], "verification": [ "Resolve the declared alias chain.", "Report an unknown consumer cache policy explicitly." ], "deliverables": [ "DNS dependency inventory." ], "rollout": "Review inventory before scheduling a cutover.", "skills": [ "DNS fundamentals" ], "fieldMix": [ { "field": "Networking", "percentage": 100 } ], "patterns": [] }, { "id": "bf6086e3-8102-4a40-bffe-a1e7b83b1e80", "key": "BDNS-102", "title": "Implement TTL-aware positive caching in the resolver fixture", "type": "TASK", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 120, "phaseId": "records", "dependsOn": [ "BDNS-101" ], "scenario": "The simulator caches every answer forever and cannot represent migration delays.", "acceptanceCriteria": [ "Expire answers using an injected clock.", "Honor the declared TTL without extending it on reads.", "Key cache entries by name and record type." ], "implementationNotes": [ "Do not use wall-clock sleeps in tests." ], "verification": [ "Serve a cached answer before expiry.", "Advance time and retrieve the changed authoritative answer." ], "deliverables": [ "Positive-cache simulator." ], "rollout": "Validate the simulator against its documented semantics before using results.", "skills": [ "Caching", "DNS" ], "fieldMix": [ { "field": "Networking", "percentage": 60 }, { "field": "Performance engineering", "percentage": 40 } ], "patterns": [] }, { "id": "cf50600f-9307-4e82-885d-1bd7185bdc21", "key": "BDNS-103", "title": "Model negative caching separately from empty address records", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "records", "dependsOn": [ "BDNS-102" ], "scenario": "A temporary missing hostname remains unavailable after its record is created.", "acceptanceCriteria": [ "Distinguish nonexistent name from no record of requested type.", "Apply declared negative-cache lifetime.", "Preserve the reason for cached negative answers." ], "implementationNotes": [ "Use explicit fixture policy rather than claiming universal resolver behavior." ], "verification": [ "Create a record after a negative lookup.", "Show recovery only after the modeled negative cache expires." ], "deliverables": [ "Negative-cache scenarios." ], "rollout": "Avoid deleting names during cutover unless negative-cache effects are accepted.", "skills": [ "DNS", "Failure analysis" ], "fieldMix": [ { "field": "Networking", "percentage": 80 }, { "field": "Site reliability", "percentage": 20 } ], "patterns": [] }, { "id": "39da833a-46b5-45ef-a09f-5f7627bd6a4c", "key": "BDNS-104", "title": "Reject alias loops and excessively deep resolution chains", "type": "BUG", "priority": "HIGH", "difficulty": "INTERMEDIATE", "estimateMinutes": 120, "phaseId": "migrate", "dependsOn": [ "BDNS-102" ], "scenario": "A mistaken alias points back to the original hostname and exhausts lookup work.", "acceptanceCriteria": [ "Track visited aliases.", "Bound chain depth and response size.", "Return a clear resolution failure without partial success." ], "implementationNotes": [ "The resolver fixture remains local and read-only." ], "verification": [ "Resolve a valid multi-hop chain.", "Reject a loop and an over-depth chain." ], "deliverables": [ "Alias validation." ], "rollout": "Validate proposed record sets before applying the synthetic change.", "skills": [ "Graph traversal", "Resource bounds" ], "fieldMix": [ { "field": "Networking", "percentage": 70 }, { "field": "Backend", "percentage": 30 } ], "patterns": [] }, { "id": "7c85c9cf-6719-4a49-af03-da492dd31022", "key": "BDNS-105", "title": "Rehearse lowering TTL before endpoint cutover", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "migrate", "dependsOn": [ "BDNS-102", "BDNS-103" ], "scenario": "Lowering TTL at the same moment as the address change does not shorten existing cached lifetimes.", "acceptanceCriteria": [ "Model caches populated before and after TTL reduction.", "Calculate the required wait under declared assumptions.", "Track old and new endpoint usage during overlap." ], "implementationNotes": [ "Do not promise that every real client respects TTL." ], "verification": [ "Simulate an appropriately staged cutover.", "Show a stale pre-change cache after an immediate cutover." ], "deliverables": [ "TTL staging rehearsal." ], "rollout": "Keep the old endpoint available through the documented overlap.", "skills": [ "Migration planning" ], "fieldMix": [ { "field": "Networking", "percentage": 60 }, { "field": "Site reliability", "percentage": 40 } ], "patterns": [] }, { "id": "1208381a-6a1e-48d8-8aba-6d74458d6151", "key": "BDNS-106", "title": "Preserve application compatibility across old and new addresses", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "migrate", "dependsOn": [ "BDNS-105" ], "scenario": "DNS propagation sends different clients to different service versions.", "acceptanceCriteria": [ "Exercise the same public contract on both endpoints.", "Preserve shared operation identity across retries.", "Reject incompatible old/new behavior before cutover." ], "implementationNotes": [ "Use synthetic requests and loopback endpoints." ], "verification": [ "Complete retries across both endpoints.", "Detect a response-contract mismatch during overlap." ], "deliverables": [ "Endpoint overlap checks." ], "rollout": "Deploy compatible service behavior before changing DNS.", "skills": [ "Compatibility", "Networking" ], "fieldMix": [ { "field": "Networking", "percentage": 40 }, { "field": "API design", "percentage": 40 }, { "field": "Quality engineering", "percentage": 20 } ], "patterns": [] }, { "id": "adbe8e8c-7b08-44dc-9a68-ff7614f15e89", "key": "BDNS-107", "title": "Distinguish resolver failure from application connection failure", "type": "STORY", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "migrate", "dependsOn": [ "BDNS-104", "BDNS-106" ], "scenario": "Operators see one generic network error for lookup failures and refused connections.", "acceptanceCriteria": [ "Classify lookup, address selection, connection, and HTTP failures.", "Record bounded timing per stage.", "Keep hostnames and request data within the declared safe diagnostic policy." ], "implementationNotes": [ "No packet payloads or credentials in generic logs." ], "verification": [ "Diagnose a local nonexistent name.", "Resolve an address then distinguish refused connection." ], "deliverables": [ "Network-stage diagnostics." ], "rollout": "Add classification before changing retry behavior.", "skills": [ "Network diagnostics" ], "fieldMix": [ { "field": "Networking", "percentage": 70 }, { "field": "Site reliability", "percentage": 30 } ], "patterns": [] }, { "id": "5cdf40a3-177e-417d-acf2-102fd280ff4f", "key": "BDNS-108", "title": "Evaluate rollback when both old and new answers remain cached", "type": "TASK", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 300, "phaseId": "assess", "dependsOn": [ "BDNS-105", "BDNS-106", "BDNS-107" ], "scenario": "Reverting the DNS record does not immediately send every client back to the old endpoint.", "acceptanceCriteria": [ "Model multiple cache ages during rollback.", "Define service compatibility and overlap requirements.", "Compare DNS rollback with routing-level containment under declared constraints." ], "implementationNotes": [ "Keep conclusions scoped to the simulated client population." ], "verification": [ "Roll back with mixed cached answers.", "Expose clients that continue using the new endpoint until expiry." ], "deliverables": [ "DNS recovery decision record." ], "rollout": "Retain both compatible endpoints until the modeled overlap and operational checks complete.", "skills": [ "Distributed systems", "Recovery" ], "fieldMix": [ { "field": "Networking", "percentage": 40 }, { "field": "Distributed systems", "percentage": 30 }, { "field": "Site reliability", "percentage": 30 } ], "patterns": [] }, { "id": "24913884-11e1-4b8c-83f1-44fb1e8843a5", "key": "BDNS-109", "title": "Check IPv4 and IPv6 record migration independently", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 180, "phaseId": "assess", "dependsOn": [ "BDNS-108" ], "scenario": "Only the IPv4 record is updated while dual-stack clients continue using the old IPv6 endpoint.", "acceptanceCriteria": [ "Track A and AAAA records separately.", "Rehearse differing cache ages by family.", "Verify contract compatibility on both local address families." ], "implementationNotes": [ "If IPv6 is unavailable locally, label that execution unverified and use deterministic fixtures." ], "verification": [ "Simulate synchronized family updates.", "Detect a stale AAAA record after A changes." ], "deliverables": [ "Dual-stack DNS cutover checks." ], "rollout": "Require family-specific review before final endpoint retirement.", "skills": [ "IPv6", "DNS" ], "fieldMix": [ { "field": "Networking", "percentage": 80 }, { "field": "Quality engineering", "percentage": 20 } ], "patterns": [] }, { "id": "21b490b7-5c22-4a1b-82d5-5cc59efb1674", "key": "BDNS-110", "title": "Write a DNS change record with cache assumptions", "type": "CHORE", "priority": "LOW", "difficulty": "FOUNDATIONAL", "estimateMinutes": 60, "phaseId": "assess", "dependsOn": [ "BDNS-109" ], "scenario": "The handoff omits when TTL was lowered and when old endpoints can be removed.", "acceptanceCriteria": [ "Record old/new values and effective times.", "List modeled cache and compatibility assumptions.", "Define endpoint retirement criteria." ], "implementationNotes": [ "Use UTC timestamps and synthetic record identities." ], "verification": [ "Follow the staged change from the record.", "Keep retirement blocked when a required client assumption is unknown." ], "deliverables": [ "DNS cutover runbook." ], "rollout": "Preserve the change record after rollback or completion.", "skills": [ "Runbooks" ], "fieldMix": [ { "field": "Networking", "percentage": 70 }, { "field": "Site reliability", "percentage": 30 } ], "patterns": [] } ] } ] }