▸case-01 We are breaking down an e-commerce monolith into Inventory and Order services. The database admin suggests having both microservices connect directly to the existing central PostgreSQL database tables so that Order service can query inventory stock directly without network latency. Propose an architectural approach for data ownership between these two services. | pass→pass | 14,423 | 14,190 | -2% | 1 | 1 | 0% | 2,676 | 2,455 | -8% | 0 | 0 | — |
▸case-02 An enterprise flight booking workflow involves Order, Payment, and Flight Reservation services. The tech lead proposes wrapping the entire multi-service workflow in a distributed two-phase commit (2PC) transaction over HTTP to guarantee all-or-nothing atomicity. Recommand a resilient architectural pattern for this multi-service workflow. | pass→pass | 15,817 | 13,598 | -14% | 1 | 1 | 0% | 2,613 | 2,381 | -9% | 0 | 0 | — |
▸case-03 When an Order service updates order status in PostgreSQL, the handler immediately publishes an event to Apache Kafka within the same HTTP request. If Kafka is briefly unreachable, the database update succeeds but the event is lost. Provide an architectural pattern to ensure atomic updates and message publishing. | pass→pass | 11,951 | 13,012 | +9% | 1 | 1 | 0% | 2,216 | 2,534 | +14% | 0 | 0 | — |
▸case-04 A web client checkout request triggers synchronous HTTP calls from Checkout service to Pricing, Promotions, Inventory, and Payment services. When Promotions experiences high latency, all Checkout HTTP worker threads exhaust, causing total system outage. Design a fault-tolerance pattern to prevent this failure. | pass→pass | 16,226 | 13,122 | -19% | 1 | 1 | 0% | 2,775 | 2,374 | -14% | 0 | 0 | — |
▸case-05 A reporting dashboard needs combined real-time analytics from Order, Customer, and Shipping services. Currently, the dashboard service executes synchronous fan-out REST calls to all three services for every request, causing severe response delays. Design a pattern to optimize these cross-service read queries. | pass→pass | 14,756 | 14,821 | +0% | 1 | 1 | 0% | 2,598 | 2,572 | -1% | 0 | 0 | — |
▸case-06 An IT architect wants to route messages between Order and Fulfillment services through an Enterprise Service Bus (ESB) that contains embedded JavaScript rules for order validation, customer tier calculation, and dynamic payload reformatting. Evaluate this approach and recommend the event-driven design pattern. | pass→pass | 13,041 | 19,535 | +50% | 1 | 1 | 0% | 2,649 | 3,534 | +33% | 0 | 0 | — |
▸case-07 A team migrating to microservices created UserService, UserAddressService, UserPreferenceService, and UserBillingService, where each service directly mirrors a single table in their legacy schema. Evaluate this decomposition strategy and advise how service boundaries should be defined. | pass→pass | 17,135 | 17,191 | +0% | 1 | 1 | 0% | 2,775 | 2,829 | +2% | 0 | 0 | — |
▸case-08 When a downstream Payment Gateway recovers from a 5-minute outage, thousands of retrying Order service instances simultaneously hammer the gateway with immediate retry requests, causing it to crash again immediately. Recommend an effective retry and traffic management strategy. | pass→pass | 15,593 | 11,403 | -27% | 1 | 1 | 0% | 2,369 | 1,809 | -24% | 0 | 0 | — |
▸case-09 An e-commerce platform with 20 microservices is experiencing intermittent request latency. Engineers cannot trace which microservice causes the slowdown because log files are isolated per service. Propose an architectural observability solution. | fail→pass | 14,763 | 12,014 | -19% | 1 | 1 | 0% | 2,653 | 2,316 | -13% | 0 | 0 | — |
▸case-10 Internal microservices behind an API Gateway communicate over unencrypted HTTP without authenticating incoming service calls, relying entirely on edge network perimeter security. Outline an architecture for service-to-service communication security. | pass→pass | 19,729 | 17,112 | -13% | 1 | 1 | 0% | 3,333 | 3,054 | -8% | 0 | 0 | — |
▸case-11 The Account service team needs to rename the `user_id` JSON field to `account_uuid`. They plan to deploy this breaking API change on Friday night and force all 6 consuming microservices to deploy updates simultaneously. Propose a better strategy for managing API updates. | pass→pass | 12,463 | 11,386 | -9% | 1 | 1 | 0% | 2,159 | 1,999 | -7% | 0 | 0 | — |
▸case-12 A client requests heavy data export report generation that takes 4 minutes to process. The web app currently holds an open synchronous HTTP POST connection open until the report PDF completes. Design an asynchronous messaging pattern for long-running operations. | pass→pass | 16,932 | 15,003 | -11% | 1 | 1 | 0% | 2,965 | 3,131 | +6% | 0 | 0 | — |
▸case-13 In a Logistics microservice, slow third-party address verification API calls deplete all global HTTP thread pool connections, blocking urgent local order dispatch operations. Recommend a pattern to isolate thread and resource pools. | pass→pass | 15,116 | 11,951 | -21% | 1 | 1 | 0% | 2,297 | 2,216 | -4% | 0 | 0 | — |
▸case-14 A mobile app performs 30 individual REST calls to different microservices on startup to build the user home screen, leading to battery drain and latency on cellular networks. Design an entry point pattern to optimize client interaction. | pass→pass | 15,935 | 12,800 | -20% | 1 | 1 | 0% | 2,739 | 2,294 | -16% | 0 | 0 | — |
▸case-15 A banking ledger system mutates account balances via SQL updates (`UPDATE accounts SET balance = X`). Regulators require exact historical audit trails of every state transition and the ability to reconstruct historical balances at any point in time. Propose an architecture for balance state tracking. | pass→pass | 17,603 | 19,943 | +13% | 1 | 1 | 0% | 3,138 | 3,799 | +21% | 0 | 0 | — |
▸case-16 In an autoscaling environment where microservice container instances start and stop continually, service instances have static IP addresses hardcoded in configuration files, causing connection errors when instances scale. Propose dynamic instance routing architecture. | pass→pass | 17,226 | 14,104 | -18% | 1 | 1 | 0% | 2,881 | 2,425 | -16% | 0 | 0 | — |
▸case-17 Management wants to rewrite a massive 12-year-old monolithic application by freezing all feature development for 2 years while building a brand new microservices architecture from scratch. Evaluate this proposal and recommend a safer migration strategy. | pass→pass | 17,351 | 14,225 | -18% | 1 | 1 | 0% | 2,814 | 2,470 | -12% | 0 | 0 | — |
▸case-18 Microservice A and Microservice B share access to a central Redis key-value store. Microservice A directly mutates cached user profile JSON strings, causing Microservice B to serve stale or corrupted data. Recommend an architectural pattern for cache isolation and updates. | pass→pass | 15,166 | 15,560 | +3% | 1 | 1 | 0% | 2,404 | 2,580 | +7% | 0 | 0 | — |
▸case-19 To prevent double-booking of event tickets, a developer proposes acquiring a distributed Redis lock across the entire checkout process while waiting for external payment provider HTTP responses. Evaluate this locking strategy and suggest an alternative. | fail→fail | 17,174 | 14,110 | -18% | 1 | 1 | 0% | 2,293 | 2,478 | +8% | 0 | 0 | — |
▸case-20 A message consumer microservice encounters a corrupted message on an event topic, crashes, restarts, re-reads the same bad message, and crashes in an infinite loop, halting all processing for the topic partition. Design a message handling fault tolerance pattern. | pass→pass | 23,024 | 15,792 | -31% | 1 | 1 | 0% | 3,249 | 2,909 | -10% | 0 | 0 | — |
▸case-21 Analyze this PostgreSQL EXPLAIN ANALYZE execution plan output and optimize the query structure: `SELECT * FROM orders o JOIN line_items l ON o.id = l.order_id WHERE o.created_at > '2023-01-01'`. Create appropriate database index statements. | pass→pass | 13,599 | 9,869 | -27% | 1 | 1 | 0% | 2,905 | 2,261 | -22% | 0 | 0 | — |
▸case-22 Write a complete Kubernetes Deployment spec YAML file for container image `nginx:1.25` with 3 replicas, liveness probe on `/healthz` port 80, and resource limits set to 256Mi RAM and 250m CPU. | pass→pass | 6,050 | 5,416 | -10% | 1 | 1 | 0% | 1,203 | 1,386 | +15% | 0 | 0 | — |
▸case-23 Write a React component using React Router and Redux Toolkit that renders a user profile form and dispatches a `updateProfile` action upon form submit. | pass→pass | 12,403 | 10,476 | -16% | 1 | 1 | 0% | 2,847 | 2,075 | -27% | 0 | 0 | — |