▸case-01 An enterprise SOAP-based billing monolith needs to be gradually replaced with modern REST microservices. Developers are tempted to update existing client applications directly to point to the new endpoints as they are built. Design the traffic control mechanism at the infrastructure edge to safely steer traffic incrementally without updating client code. | pass→pass | 19,981 | 18,854 | -6% | 1 | 1 | 0% | 3,294 | 3,479 | +6% | 0 | 0 | — |
▸case-02 During the migration of a legacy monolithic ordering system to a microservice, order writes must occur in the modern service while legacy downstream reporting systems still read directly from the monolithic database. Developers suggest nightly bulk SQL exports to keep tables in sync. Provide an architecture that keeps data synchronized near real-time. | pass→pass | 15,471 | 17,205 | +11% | 1 | 1 | 0% | 2,525 | 2,668 | +6% | 0 | 0 | — |
▸case-03 An aging e-commerce application has a single monolithic relational database where the 'users' table is directly joined in SQL queries by inventory, checkout, and shipping modules. Engineers suggest splitting services based on database table clusters. Define the proper approach for identifying service boundaries. | pass→pass | 15,435 | 12,224 | -21% | 1 | 1 | 0% | 2,414 | 2,195 | -9% | 0 | 0 | — |
▸case-04 A legacy Java monolith returns XML payloads with camelCase tags to mobile clients. The newly extracted user service emits JSON with snake_case keys. Mobile teams refuse to release a client update. How should the API facade handle this incompatibility? | fail→pass | 14,519 | 17,091 | +18% | 1 | 1 | 0% | 2,608 | 3,141 | +20% | 0 | 0 | — |
▸case-05 A team is preparing to decompose a 15-year-old C++ monolith. They rely solely on static code analysis of header imports to determine module coupling. Explain what complementary analysis must be performed to build a accurate dependency map. | pass→pass | 16,655 | 16,009 | -4% | 1 | 1 | 0% | 2,641 | 2,473 | -6% | 0 | 0 | — |
▸case-06 A newly strangled account management microservice begins throwing 500 errors for 2% of traffic routed through the edge proxy. The operational team wants to redeploy the old monolithic code branch. Describe the instant traffic routing mitigation. | pass→pass | 11,005 | 11,516 | +5% | 1 | 1 | 0% | 1,830 | 1,976 | +8% | 0 | 0 | — |
▸case-07 Engineers are creating two new microservices, CustomerService and OrderService, from a legacy codebase. They plan to have both microservices connect directly to the legacy PostgreSQL instance and read/write to the 'customers' table. Evaluate this decision. | pass→pass | 12,958 | 12,267 | -5% | 1 | 1 | 0% | 2,181 | 1,828 | -16% | 0 | 0 | — |
▸case-08 Legacy web clients authenticate using stateful HTTP session cookies managed by the monolith. New microservices behind the API facade require JWT bearer tokens. How should the API facade manage client authentication during transition? | pass→pass | 14,484 | 16,862 | +16% | 1 | 1 | 0% | 2,567 | 3,180 | +24% | 0 | 0 | — |
▸case-09 Static analysis reveals a cyclic dependency between the legacy Inventory module and Payment module. Developers want to merge them into a single microservice to avoid breaking the cycle. Provide the refactoring solution. | pass→pass | 15,496 | 13,062 | -16% | 1 | 1 | 0% | 2,412 | 2,394 | -1% | 0 | 0 | — |
▸case-10 A legacy product catalog receives 50,000 read requests per second. The team wants to switch all read traffic to the new microservice immediately after deployment. Detail the low-risk migration sequence for read traffic. | fail→pass | 18,662 | 13,329 | -29% | 1 | 1 | 0% | 2,807 | 2,438 | -13% | 0 | 0 | — |
▸case-11 An engineering department needs to select the first candidate module to extract from a large monolith. Some engineers argue for picking the simplest, lowest-traffic utility module. Outline the criteria for selecting high-impact extraction candidates. | pass→pass | 11,371 | 14,096 | +24% | 1 | 1 | 0% | 2,155 | 1,981 | -8% | 0 | 0 | — |
▸case-16 An organization needs to support legacy mobile app v1 clients using `/api/v1/checkout` alongside modern web app clients using `/api/v2/checkout`. How should this route mapping be managed without duplicating backend logic? | pass→pass | 15,152 | 12,271 | -19% | 1 | 1 | 0% | 2,448 | 2,452 | +0% | 0 | 0 | — |
▸case-12 After introducing a new single-page frontend application, traffic spikes from client polling begin overloading legacy monolith endpoints exposed through the API gateway. Where should protection mechanisms be enforced? | pass→fail | 12,448 | 11,773 | -5% | 1 | 1 | 0% | 1,979 | 2,061 | +4% | 0 | 0 | — |
▸case-13 When splitting a monolithic codebase into microservices, developers discover a shared common utility library containing domain models, database helper methods, and string utilities referenced by all modules. How should this library be handled? | pass→pass | 15,180 | 13,595 | -10% | 1 | 1 | 0% | 2,619 | 2,316 | -12% | 0 | 0 | — |
▸case-14 To validate a newly strangled payment processing microservice, the team runs dual-writes from the API gateway to both monolith and microservice. How do they verify that data written to both systems remains consistent? | pass→pass | 14,176 | 15,382 | +9% | 1 | 1 | 0% | 2,265 | 2,396 | +6% | 0 | 0 | — |
▸case-15 A newly extracted Inventory service needs to publish an event when stock levels change so the legacy monolith can update its search index. Developers suggest using a distributed 2-phase commit transaction across the database and message broker. Provide a resilient alternative pattern. | pass→pass | 9,753 | 11,005 | +13% | 1 | 1 | 0% | 1,735 | 2,138 | +23% | 0 | 0 | — |
▸case-17 Before modernizing a 500,000-line monolithic codebase, architects want to avoid migrating unneeded functionality. Code coverage reports from unit tests show 40% unused code. How should unused production paths be identified? | pass→pass | 14,144 | 12,573 | -11% | 1 | 1 | 0% | 2,346 | 2,809 | +20% | 0 | 0 | — |
▸case-18 A legacy PHP application stores user session data in local server memory (`/tmp` session files). The modernization plan involves strangling web routes using a cluster of microservices behind a load balancer. What prerequisite refactoring is required? | pass→pass | 13,278 | 11,073 | -17% | 1 | 1 | 0% | 2,366 | 2,096 | -11% | 0 | 0 | — |
▸case-19 During modernizing an insurance claims monolith, auditors require a complete chronological history of all status changes for extracted claim records. How should the modern service record state modifications? | pass→pass | 13,640 | 15,378 | +13% | 1 | 1 | 0% | 2,285 | 2,466 | +8% | 0 | 0 | — |
▸case-20 A startup is building a brand new ride-sharing application from scratch with zero legacy code or existing infrastructure. Design a cloud-native backend architecture using modern serverless containers and managed databases on AWS. | pass→pass | 18,285 | 17,504 | -4% | 1 | 1 | 0% | 3,664 | 3,068 | -16% | 0 | 0 | — |
▸case-21 A legacy web application uses HTML tables and CSS `float: left` positioning for its core dashboard page layout. Recommend modern CSS features to refactor the layout for responsive design across mobile and desktop screens. | pass→pass | 14,794 | 18,242 | +23% | 1 | 1 | 0% | 2,787 | 3,557 | +28% | 0 | 0 | — |
▸case-22 A C networking daemon allocates memory with `malloc()` inside a client connection handling loop but fails to release memory when clients abruptly disconnect. How should the developer diagnose and fix this memory leak using standard Linux tools? | pass→pass | 15,215 | 17,966 | +18% | 1 | 1 | 0% | 2,840 | 3,487 | +23% | 0 | 0 | — |