{ "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": "40608db5-35cd-4637-b5a2-3043fef5b1b7", "key": "AADMIT", "title": "Design admission control for scheduled report generation", "field": "System design", "summary": "Define fair scheduling, bounded work and recovery for a report service.", "context": "A fictional analytics product lets customers schedule expensive reports at the top of the hour. The API remains available only if report work is admitted and cancelled predictably.", "stack": [ "TypeScript", "PostgreSQL", "BullMQ" ], "prerequisites": [ "Create a local scheduler model and synthetic report jobs.", "Use fake execution providers; no customer queries or candidate code run on worker hosts." ], "developerValue": "Practice workload modeling, fairness and cancellation architecture.", "companyValue": "Review controllable operating costs and predictable customer-facing overload behavior.", "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": "load", "title": "Define load and fairness", "goal": "Make demand and service objectives explicit." }, { "id": "control", "title": "Specify admission and work ownership", "goal": "Bound queues, retries and cancellation." }, { "id": "stress", "title": "Challenge overload behavior", "goal": "Model burst recovery and review operating limits." } ], "tickets": [ { "id": "8ba0ed0d-54d5-43f9-9a53-6e0f0300a086", "key": "AADMIT-101", "title": "Build a report arrival model that includes top-of-hour bursts", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 90, "phaseId": "load", "dependsOn": [], "scenario": "Average reports per minute looks harmless, but nearly every customer chooses 09:00 for its daily report.", "acceptanceCriteria": [ "Separate average arrival rate from burst size.", "State hypothetical report duration and size classes.", "Include timezone scheduling assumptions." ], "implementationNotes": [ "Create a deterministic synthetic one-day schedule." ], "verification": [ "Count average arrivals and the largest one-minute burst.", "Move all schedules to one instant and show the peak changes despite equal daily volume." ], "deliverables": [ "Arrival model and reproducible schedule generator" ], "rollout": "Review the model before queue sizing; revise assumptions when schedule usage is measured.", "skills": [ "Workload modeling", "Scheduling" ], "fieldMix": [ { "field": "System design", "percentage": 50 }, { "field": "Performance engineering", "percentage": 50 } ], "patterns": [] }, { "id": "fa744788-c136-4ecc-afd1-2b1050ad1a5b", "key": "AADMIT-102", "title": "Define customer-visible report states and overload responses", "type": "TASK", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "load", "dependsOn": [ "AADMIT-101" ], "scenario": "The API returns accepted for jobs that may wait indefinitely, so customers repeatedly click generate.", "acceptanceCriteria": [ "Distinguish rejected, queued, running and terminal states.", "Specify bounded queue age and a retryable admission response.", "Define what acceptance durably guarantees." ], "implementationNotes": [ "Use explicit state transitions and stable job identities." ], "verification": [ "Trace an admitted report to its durable queue state.", "Reject an over-capacity request without creating a phantom report." ], "deliverables": [ "Admission response contract and state table" ], "rollout": "Review the contract before accepting schedules; keep overload behavior explicit in the prototype.", "skills": [ "API design", "State modeling" ], "fieldMix": [ { "field": "API design", "percentage": 50 }, { "field": "System design", "percentage": 30 }, { "field": "Backend", "percentage": 20 } ], "patterns": [] }, { "id": "1a98ca58-7afc-425d-8917-3dd341022e3c", "key": "AADMIT-103", "title": "Record the fairness decision for small and large report tenants", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 120, "phaseId": "load", "dependsOn": [ "AADMIT-101", "AADMIT-102" ], "scenario": "A single tenant's weekly exports occupy every available slot while small interactive reports wait behind them.", "acceptanceCriteria": [ "Compare FIFO, per-tenant limits and weighted scheduling.", "Define fairness and starvation expectations.", "Document how unknown report cost is classified." ], "implementationNotes": [ "Use a small synthetic tenant set and avoid hiring or user scoring." ], "verification": [ "Evaluate a mixed small/large workload against the chosen rule.", "Show the behavior when one tenant continuously submits work." ], "deliverables": [ "Fairness decision record" ], "rollout": "Review the chosen policy with the workload model; retain configuration for bounded tuning.", "skills": [ "Scheduling tradeoffs", "Fairness" ], "fieldMix": [ { "field": "System design", "percentage": 60 }, { "field": "Distributed systems", "percentage": 40 } ], "patterns": [] }, { "id": "e8b6d914-6122-4995-bfc6-0d61adbc8d55", "key": "AADMIT-104", "title": "Specify transactional report admission with deterministic job identities", "type": "STORY", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "control", "dependsOn": [ "AADMIT-102", "AADMIT-103" ], "scenario": "A scheduler creates report rows but loses queue publication, leaving accepted work with no execution path.", "acceptanceCriteria": [ "Commit admission and outbox fact atomically.", "Bind job identity to schedule occurrence or request key.", "Make repeated dispatch resolve one logical job." ], "implementationNotes": [ "Keep lifecycle authority in the durable service boundary." ], "verification": [ "Crash after admission commit and recover dispatch.", "Replay the same scheduled occurrence and count one report." ], "deliverables": [ "Admission/outbox contract and crash probe" ], "rollout": "Prototype with a fake executor; stop new admission if durable dispatch cannot be recorded.", "skills": [ "Transactional outbox", "Idempotency" ], "fieldMix": [ { "field": "System design", "percentage": 40 }, { "field": "Distributed systems", "percentage": 40 }, { "field": "Database engineering", "percentage": 20 } ], "patterns": [] }, { "id": "b587096d-ae53-4945-a9c5-d734cb9ccf09", "key": "AADMIT-105", "title": "Design cancellation ownership for queued and running reports", "type": "TASK", "priority": "MEDIUM", "difficulty": "EXPERT", "estimateMinutes": 300, "phaseId": "control", "dependsOn": [ "AADMIT-102", "AADMIT-104" ], "scenario": "A user cancels a report, but the worker later publishes a completed artifact and overwrites the cancellation status.", "acceptanceCriteria": [ "Define cancellation request versus confirmed stop.", "Fence stale completion against current generation and state.", "Specify cleanup ownership for incomplete artifacts." ], "implementationNotes": [ "Use a provider cancellation contract; do not kill host processes arbitrarily." ], "verification": [ "Cancel queued work and verify no execution begins.", "Race cancellation with completion and preserve the declared single terminal outcome." ], "deliverables": [ "Cancellation protocol and race model" ], "rollout": "Canary cancellation in the local provider; retain unresolved stop status when provider confirmation is unavailable.", "skills": [ "Cancellation design", "Concurrency" ], "fieldMix": [ { "field": "System design", "percentage": 50 }, { "field": "Distributed systems", "percentage": 30 }, { "field": "Storage systems", "percentage": 20 } ], "patterns": [] }, { "id": "4f1d61c1-ad38-4817-9864-7c1c163ac668", "key": "AADMIT-106", "title": "Bound retries so failing reports cannot consume the entire service", "type": "TASK", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 210, "phaseId": "control", "dependsOn": [ "AADMIT-103", "AADMIT-104", "AADMIT-105" ], "scenario": "A malformed report fails immediately and retries faster than healthy reports can start.", "acceptanceCriteria": [ "Define retry count, backoff and elapsed-time budgets.", "Classify permanent versus retryable failure explicitly.", "Keep retry work inside tenant and global admission limits." ], "implementationNotes": [ "Use deterministic fake time and bounded jitter inputs." ], "verification": [ "Retry a transient failure within the declared budget.", "Feed a permanent failure and verify it cannot form a tight retry loop." ], "deliverables": [ "Retry-budget model and scheduling probe" ], "rollout": "Enable bounded retries for synthetic jobs; suspend a failing class if classification is uncertain.", "skills": [ "Retry policy", "Resource budgets" ], "fieldMix": [ { "field": "System design", "percentage": 50 }, { "field": "Site reliability", "percentage": 30 }, { "field": "Platform engineering", "percentage": 20 } ], "patterns": [] }, { "id": "b9ec6557-fb1b-43af-b467-f6ab1c2f0db5", "key": "AADMIT-107", "title": "Choose where report artifacts become authoritative", "type": "STORY", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 180, "phaseId": "control", "dependsOn": [ "AADMIT-104", "AADMIT-105" ], "scenario": "A worker uploads a partial file and the API exposes its object key before completion checks finish.", "acceptanceCriteria": [ "Stage artifacts under a job generation.", "Publish only after verified storage identity and guarded completion.", "Keep incomplete or stale-generation artifacts inaccessible." ], "implementationNotes": [ "Separate object upload from user-visible report publication." ], "verification": [ "Publish a verified synthetic artifact for the active job.", "Complete an older generation and verify it cannot replace the visible result." ], "deliverables": [ "Artifact publication boundary and contract probe" ], "rollout": "Prototype with local storage; keep staged objects private until finalization succeeds.", "skills": [ "Storage lifecycle", "System boundaries" ], "fieldMix": [ { "field": "Storage systems", "percentage": 50 }, { "field": "System design", "percentage": 30 }, { "field": "Security", "percentage": 20 } ], "patterns": [] }, { "id": "b1c2d8ac-ee40-4ba1-88e8-77c6338b3ad0", "key": "AADMIT-108", "title": "Calculate burst drain time with fairness and retry reservations", "type": "TASK", "priority": "MEDIUM", "difficulty": "EXPERT", "estimateMinutes": 300, "phaseId": "stress", "dependsOn": [ "AADMIT-101", "AADMIT-103", "AADMIT-106" ], "scenario": "Operations wants a queue-age target, but the capacity spreadsheet assumes every slot is always available for first attempts.", "acceptanceCriteria": [ "Model concurrency, service-time classes and reserved retry capacity.", "Calculate per-tenant wait under the selected fairness rule.", "Show when queue-age targets cannot be met." ], "implementationNotes": [ "Use hypothetical durations and an executable deterministic simulation." ], "verification": [ "Simulate the declared top-of-hour burst.", "Double expensive reports and report target violations without inventing a speedup." ], "deliverables": [ "Queue simulation and capacity worksheet" ], "rollout": "Use the model to propose reviewed limits; validate assumptions with real isolated measurements before deployment.", "skills": [ "Queueing analysis", "Capacity planning" ], "fieldMix": [ { "field": "Performance engineering", "percentage": 60 }, { "field": "System design", "percentage": 40 } ], "patterns": [] }, { "id": "be761ff0-1cd2-4c43-a5cc-5e27c504bcf4", "key": "AADMIT-109", "title": "Rehearse scheduler restart while reports are queued and running", "type": "TASK", "priority": "MEDIUM", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "stress", "dependsOn": [ "AADMIT-104", "AADMIT-105", "AADMIT-107", "AADMIT-108" ], "scenario": "The scheduling process restarts during a burst, and the design must explain which work is resumed, reconciled or left uncertain.", "acceptanceCriteria": [ "Recover queued ownership from durable identities.", "Reconcile running jobs through provider status before retry.", "Preserve accepted artifacts and terminal outcomes." ], "implementationNotes": [ "Inject failures in a local state model and fake provider." ], "verification": [ "Restart with queued and completed synthetic jobs and converge correctly.", "Restart with an unknown provider outcome and keep it unresolved instead of duplicating work." ], "deliverables": [ "Restart drill and recovery trace" ], "rollout": "Run before accepting real schedules; pause admissions if recovery cannot establish work ownership.", "skills": [ "Recovery protocols", "Fault injection" ], "fieldMix": [ { "field": "System design", "percentage": 40 }, { "field": "Distributed systems", "percentage": 40 }, { "field": "Site reliability", "percentage": 20 } ], "patterns": [] }, { "id": "c141387e-1daa-44c7-8448-1e940e3ede6c", "key": "AADMIT-110", "title": "Write the report-service operating contract for design approval", "type": "CHORE", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 90, "phaseId": "stress", "dependsOn": [ "AADMIT-102", "AADMIT-108", "AADMIT-109" ], "scenario": "A launch checklist says scalable reporting without naming admission limits, cancellation guarantees or unavailable-provider behavior.", "acceptanceCriteria": [ "Summarize admitted workload, fairness and bounded queue behavior.", "Link each guarantee to a model or probe.", "List deferred execution-provider and production-measurement work." ], "implementationNotes": [ "Keep design approval separate from production readiness." ], "verification": [ "Trace a queue-age target to its simulation assumptions.", "Trace provider unavailability to a documented pending or rejected outcome." ], "deliverables": [ "Operating contract and architecture review notes" ], "rollout": "Review before infrastructure commitment; update limits when measurement evidence replaces assumptions.", "skills": [ "Operational design", "Technical communication" ], "fieldMix": [ { "field": "System design", "percentage": 70 }, { "field": "Site reliability", "percentage": 30 } ], "patterns": [] } ] } ] }