▸case-17 Before drafting any code or database schemas for a system refactoring, what initial analysis steps must be performed when applying CQRS methodology to an enterprise application? Provide the initial assessment requirements. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-06 A logistics platform is refactoring its API payload structures for CQRS. The engineering team submitted proposed payload types like `UpdateShipmentTableDTO` with generic field maps. How should command objects be named and structured in a CQRS architecture? Provide a design recommendation. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-05 In an online catalog application using CQRS, item updates are processed by the write model. The frontend search relies on an Elasticsearch cluster for quick filtering. What synchronization mechanism should bridge the write store updates to the Elasticsearch search store? Answer with a technical proposal. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-03 Our startup team has a single PostgreSQL instance and zero DevOps capacity to manage secondary databases, event brokers, or background projection synchronization workers. An advisor suggested splitting the app into CQRS command and query stores. Provide a technical assessment on whether to adopt CQRS under these constraints. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-08 A message broker delivers domain events to read model projection consumers using at-least-once delivery. During network retransmissions, duplicate events cause duplicate entries in the query database. What structural design requirement must be implemented in the projection consumers? Provide a technical resolution. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-07 When a user submits a blog post in a CQRS system, the web application immediately performs a GET request to the query database, but the newly created post does not appear because read projection synchronization takes 200 milliseconds. How should the application interface handle this eventual consistency gap? Provide a user experience design solution. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-04 An e-commerce platform processes high-volume order submissions with strict state transition validation, while a reporting panel queries order history at 20,000 requests per second. The team currently uses a single heavy SQL database model with complex JOINs for both operations, causing severe lock contention. Provide a high-level system architecture design recommendation. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-15 A developer working on user account creation suggests that the command handler should query the eventually consistent Elasticsearch read store to check whether an email address is already registered before processing the `RegisterUser` command. How should consistency-critical invariants be validated in CQRS? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-14 While streaming domain events into a MongoDB read model projection, a malformed payload causes the projection worker to throw an uncaught exception, stalling the entire event stream processor. How should the projection handler process corrupted or unparseable events? Provide an exception handling strategy. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-02 Our banking transaction system processes real-time ledger balance updates where strict immediate ACID consistency across all database reads and writes is legally required on every single request. A designer proposed using eventually consistent CQRS projections for account balance views. Provide an architectural review decision. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-16 A REST API design team is implementing CQRS endpoints. They propose that `POST /orders` should synchronously process the command, query the MongoDB read projection, and return the complete populated order query object in the HTTP 200 response body. How should command API endpoints be designed in CQRS? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-22 Nightly BI reporting queries cause severe lock contention and slow down customer checkout transactions because both hit the same relational database. How should the system architecture resolve this reporting bottleneck? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-13 A social platform has heavy ACID transaction write requirements for financial ledger entries, but its read traffic demands fast geo-spatial proximity searches and full-text querying across millions of posts. The lead architect insists both workloads must share the same PostgreSQL table schema. What data storage architecture decision should be made under CQRS? | fail→pass | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-18 An application uses event sourcing as its write mechanism, storing state strictly as a sequence of immutable domain events. How should read queries be served efficiently in this event-sourced system? Provide a system architecture design recommendation. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-12 In a CQRS system, the write service saves entity updates to PostgreSQL and then publishes domain events to Kafka. When Kafka is temporarily unavailable, PostgreSQL updates commit but events are lost, causing read projections to fall out of sync permanently. What pattern should be implemented to guarantee reliable event publication from the write store? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-19 A domain event `OrderPlaced` evolved from version 1 to version 2 by renaming fields and adding required data. Historical v1 events in the event store fail when processed by current projection handlers. How should projection pipelines handle historical event schema changes? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-11 A software developer working on a CQRS system proposes placing domain invariant validation rules (e.g., checking if account balance is sufficient before withdrawal) inside the background projection worker that updates the read database. Where should domain invariant validation actually be performed? Provide an architectural guidance note. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-01 We are building an internal admin tool to manage employee phone numbers and office locations for 50 users. An engineer wants to set up separate Command and Query microservices with event projections to handle this data. Provide an architectural recommendation in a short design note. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-09 A deployment bug in a CQRS system caused the Elasticsearch read projection to drop several fields for three days. The primary write store remains completely undamaged and accurate. How should the engineering team restore the corrupt Elasticsearch query model? Provide a recovery procedure. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-10 An executive dashboard requires rendering user metrics compiled from 12 related entities. Currently, every HTTP request triggers a multi-table JOIN query against the primary OLTP database, leading to 3-second response times. How should the query model be structured in CQRS to optimize this scenario? Provide a query model design recommendation. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-20 In an event-sourced command aggregate, recalculating current state requires replaying over 50,000 historic events on every command execution, causing severe latency degradation. How should write model performance be optimized for long-lived aggregates? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-21 The Customer Support team needs real-time access to fulfillment status data owned by the Warehouse service. The support lead proposes querying the Warehouse team's SQL tables directly over cross-database links. How should cross-boundary data read access be handled using CQRS? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |