{ "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": "31722a2e-299d-4a44-963b-b65b13ee8f6f", "key": "AREGION", "title": "Design regional reads without promising impossible failover", "field": "System design", "summary": "Specify consistency, routing and recovery for a regional customer read experience.", "context": "A fictional logistics dashboard serves distant customers from one primary region. Stakeholders want faster reads and outage recovery but have not agreed which data may be stale.", "stack": [ "TypeScript", "PostgreSQL", "HTTP" ], "prerequisites": [ "Create a local primary/replica simulator and synthetic shipment records.", "Use local models; no multi-region infrastructure is provisioned." ], "developerValue": "Practice consistency tradeoffs, failover authority and recovery assumptions.", "companyValue": "Review regional availability proposals with explicit data-loss and staleness limits.", "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": "requirements", "title": "Classify regional behavior", "goal": "Define which reads and writes need freshness." }, { "id": "protocol", "title": "Specify routing authority", "goal": "Make routing, failover and retry contracts testable." }, { "id": "recovery", "title": "Challenge recovery promises", "goal": "Model outages and reconcile divergent observations." } ], "tickets": [ { "id": "dbd3755c-2ae6-4cd4-81c4-fe2403206832", "key": "AREGION-101", "title": "Classify shipment reads by tolerated staleness", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 90, "phaseId": "requirements", "dependsOn": [], "scenario": "The regional-read proposal treats a public tracking estimate and an address-change confirmation as equally cacheable.", "acceptanceCriteria": [ "List read classes with explicit hypothetical freshness limits.", "Require fresh authority for security and mutation confirmation.", "Document unknown product requirements separately." ], "implementationNotes": [ "Use a synthetic status timeline with version numbers." ], "verification": [ "Assign a declared budget to public tracking.", "Show why address-change confirmation needs its accepted version." ], "deliverables": [ "Read-consistency matrix" ], "rollout": "Review the matrix before routing changes; leave unresolved classes on primary reads.", "skills": [ "Consistency requirements", "Product reasoning" ], "fieldMix": [ { "field": "System design", "percentage": 60 }, { "field": "Distributed systems", "percentage": 40 } ], "patterns": [] }, { "id": "3dfbebaf-31e4-4ee6-9406-977261fa098e", "key": "AREGION-102", "title": "Calculate regional latency contributions with stated assumptions", "type": "TASK", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "requirements", "dependsOn": [ "AREGION-101" ], "scenario": "A proposal promises a faster dashboard without separating network time, database time and sequential request dependencies.", "acceptanceCriteria": [ "Break one page load into serial and parallel operations.", "Use named hypothetical network and service-time values.", "Show sensitivity to an additional cross-region round trip." ], "implementationNotes": [ "Label every unmeasured input as an assumption." ], "verification": [ "Calculate two routes with the same service-time assumptions.", "Add a required primary check and show its effect on the budget." ], "deliverables": [ "Latency worksheet and dependency diagram" ], "rollout": "Use the calculation to prioritize probes; replace assumptions with observations before choosing deployment.", "skills": [ "Latency modeling", "Critical-path analysis" ], "fieldMix": [ { "field": "Performance engineering", "percentage": 50 }, { "field": "System design", "percentage": 30 }, { "field": "Networking", "percentage": 20 } ], "patterns": [] }, { "id": "702d744a-a9b3-4873-b80e-faee1305d2fd", "key": "AREGION-103", "title": "Record the decision between regional caching and replica reads", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 120, "phaseId": "requirements", "dependsOn": [ "AREGION-101", "AREGION-102" ], "scenario": "The team jumps to database replicas when a scoped cache might cover the tolerated-staleness tracking view.", "acceptanceCriteria": [ "Compare invalidation, freshness, failure and operational costs.", "Keep sensitive and read-after-write paths explicit.", "Name a workload or consistency change that revisits the choice." ], "implementationNotes": [ "Do not assume an additional region is free or already configured." ], "verification": [ "Evaluate both options against one tracking read.", "Evaluate an authorization change and reject an option that cannot enforce it." ], "deliverables": [ "Regional-read architecture decision" ], "rollout": "Review using the consistency matrix; implement only the smallest local prototype selected.", "skills": [ "Architecture decisions", "Caching tradeoffs" ], "fieldMix": [ { "field": "System design", "percentage": 50 }, { "field": "Database engineering", "percentage": 30 }, { "field": "Distributed systems", "percentage": 20 } ], "patterns": [] }, { "id": "8b0acb5f-cb7c-46bd-ac47-65fca3efa811", "key": "AREGION-104", "title": "Define a read-after-write token for shipment changes", "type": "STORY", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 210, "phaseId": "protocol", "dependsOn": [ "AREGION-101", "AREGION-103" ], "scenario": "A user changes a delivery note, then a regional read immediately shows the previous text.", "acceptanceCriteria": [ "Mutation returns an accepted version token.", "A subsequent read must meet that version or use a fresh source.", "Tokens are bound to tenant and resource." ], "implementationNotes": [ "Implement a small local routing model, not a new replication engine." ], "verification": [ "Write version 4 while the replica has version 3 and route correctly.", "Reuse another tenant's token and reject it without exposing state." ], "deliverables": [ "Read-version contract and routing tests" ], "rollout": "Canary the routing model in a local client; fall back to primary reads when freshness cannot be established.", "skills": [ "Read-your-writes", "Routing" ], "fieldMix": [ { "field": "Distributed systems", "percentage": 60 }, { "field": "System design", "percentage": 40 } ], "patterns": [] }, { "id": "5832f9ff-4d05-49a3-ba75-6cfe8656cad9", "key": "AREGION-105", "title": "Fence regional write authority before promoting a standby", "type": "TASK", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 360, "phaseId": "protocol", "dependsOn": [ "AREGION-104" ], "scenario": "An outage runbook says promote the standby but never explains how the unreachable former primary loses authority.", "acceptanceCriteria": [ "Define one durable authority epoch and promotion preconditions.", "Reject commands using an old epoch.", "Describe the availability tradeoff when fencing cannot be confirmed." ], "implementationNotes": [ "Use a local two-writer model; do not claim split-brain prevention without enforced fencing." ], "verification": [ "Promote a new epoch and accept only the new writer.", "Let the old writer recover and reject its stale-epoch command." ], "deliverables": [ "Failover authority protocol and fencing probe" ], "rollout": "Require the probe before any real failover procedure; refuse promotion when authority is ambiguous.", "skills": [ "Fencing", "Consistency" ], "fieldMix": [ { "field": "Distributed systems", "percentage": 60 }, { "field": "System design", "percentage": 40 } ], "patterns": [] }, { "id": "444112ca-52b5-42d3-b42d-161f463da926", "key": "AREGION-106", "title": "Preserve command identity across a regional routing retry", "type": "TASK", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "protocol", "dependsOn": [ "AREGION-104", "AREGION-105" ], "scenario": "A gateway retries an update in another region after losing the response, potentially applying the shipment change twice.", "acceptanceCriteria": [ "Use a stable command key across routing attempts.", "Bind the key to target, actor and canonical input.", "Return unknown until committed status can be resolved safely." ], "implementationNotes": [ "Do not infer an absent commit from a connection timeout." ], "verification": [ "Lose the response after commit and resolve one logical change.", "Change input under the same key and return conflict." ], "deliverables": [ "Cross-route command contract and timeout probe" ], "rollout": "Use the contract in the local gateway prototype; suspend retries if deduplication authority is unavailable.", "skills": [ "Idempotency", "Distributed failure" ], "fieldMix": [ { "field": "Distributed systems", "percentage": 50 }, { "field": "System design", "percentage": 30 }, { "field": "Backend", "percentage": 20 } ], "patterns": [] }, { "id": "2a57afe0-45ef-4146-911d-5f44deb93e62", "key": "AREGION-107", "title": "Define regional fallback for unavailable authorization freshness", "type": "TASK", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 210, "phaseId": "protocol", "dependsOn": [ "AREGION-101", "AREGION-105", "AREGION-106" ], "scenario": "A regional endpoint can read cached shipment data but cannot confirm whether the requesting account's access was revoked.", "acceptanceCriteria": [ "Separate data freshness from authorization freshness.", "Deny protected reads when required authority is unavailable.", "Keep public tracking behavior separately bounded by its policy." ], "implementationNotes": [ "Model access revocation with synthetic identities." ], "verification": [ "Serve a permitted public tracking response during primary loss.", "Revoke a protected reader and verify the regional route does not use stale permission." ], "deliverables": [ "Authorization fallback matrix and denial probe" ], "rollout": "Keep protected reads on fresh authority until the regional adapter meets the contract.", "skills": [ "Authorization consistency", "Fail-closed design" ], "fieldMix": [ { "field": "Security", "percentage": 50 }, { "field": "System design", "percentage": 30 }, { "field": "Distributed systems", "percentage": 20 } ], "patterns": [] }, { "id": "d4c6f7dc-1631-404d-8f68-24651633012a", "key": "AREGION-108", "title": "Model recovery-point and recovery-time limits for a regional outage", "type": "TASK", "priority": "MEDIUM", "difficulty": "EXPERT", "estimateMinutes": 300, "phaseId": "recovery", "dependsOn": [ "AREGION-102", "AREGION-105", "AREGION-106" ], "scenario": "A stakeholder asks for zero data loss and immediate recovery even when replication is asynchronous and the primary is unreachable.", "acceptanceCriteria": [ "Define what RPO and RTO mean for the chosen workload.", "Calculate loss and recovery bounds from explicit lag and detection assumptions.", "Identify guarantees the design cannot currently provide." ], "implementationNotes": [ "Use hypothetical numbers and separate targets from measured results." ], "verification": [ "Calculate the declared outage scenario with bounded lag.", "Remove the lag bound and show that a finite loss guarantee is unsupported." ], "deliverables": [ "Recovery objectives worksheet" ], "rollout": "Review targets before infrastructure approval; revise guarantees when provider constraints differ.", "skills": [ "Recovery objectives", "Risk analysis" ], "fieldMix": [ { "field": "Site reliability", "percentage": 50 }, { "field": "System design", "percentage": 30 }, { "field": "Distributed systems", "percentage": 20 } ], "patterns": [] }, { "id": "144d5435-f3a9-48b6-af03-0aa04138dc13", "key": "AREGION-109", "title": "Reconcile divergent regional observations after connectivity returns", "type": "TASK", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 180, "phaseId": "recovery", "dependsOn": [ "AREGION-104", "AREGION-105", "AREGION-108" ], "scenario": "Support receives screenshots with different shipment states after an outage and needs to explain which accepted version is authoritative.", "acceptanceCriteria": [ "Compare accepted command versions and authority epochs.", "Preserve stale observations as observations, not new writes.", "Flag missing authoritative history as unresolved." ], "implementationNotes": [ "Build a read-only synthetic reconciliation report." ], "verification": [ "Reconcile two observed versions against the accepted command log.", "Remove an authority segment and report an explicit gap." ], "deliverables": [ "Regional reconciliation script" ], "rollout": "Run read-only after the local outage drill; avoid repair writes until authority is resolved.", "skills": [ "Reconciliation", "Provenance" ], "fieldMix": [ { "field": "Distributed systems", "percentage": 50 }, { "field": "System design", "percentage": 30 }, { "field": "Data engineering", "percentage": 20 } ], "patterns": [] }, { "id": "77ac7a28-0862-42e5-b269-53d2cf9d8829", "key": "AREGION-110", "title": "Write the staged regional-read adoption and rollback plan", "type": "CHORE", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 120, "phaseId": "recovery", "dependsOn": [ "AREGION-103", "AREGION-107", "AREGION-109" ], "scenario": "The architecture review approves a limited regional tracking view, but the rollout ticket still says switch all traffic.", "acceptanceCriteria": [ "Start with the approved read class and synthetic cohort.", "Define freshness and denial checks before wider routing.", "Rollback by restoring primary routing without rewriting accepted data." ], "implementationNotes": [ "Include unresolved dependencies as explicit blockers." ], "verification": [ "Walk a permitted tracking request through the proposed rollout.", "Trigger stale authorization and verify protected traffic stays on the declared safe path." ], "deliverables": [ "Regional adoption plan and decision checklist" ], "rollout": "Review the plan with the local simulator; retain a primary-routing override for recovery.", "skills": [ "Rollout design", "Architecture communication" ], "fieldMix": [ { "field": "System design", "percentage": 60 }, { "field": "Platform engineering", "percentage": 40 } ], "patterns": [] } ] } ] }