▸case-23 A deployment pod status shows `CrashLoopBackOff` with logs stating `fatal error: missing DB_HOST environment variable`. The quick suggestion was to hardcode the DB_HOST IP directly inside the application binary. Diagnose and resolve. | pass→pass | 10,627 | 11,786 | +11% | 1 | 1 | 0% | 1,966 | 2,506 | +27% | 0 | 0 | — |
▸case-04 Our Express REST API crashes with 'UnhandledPromiseRejectionWarning: TypeError: Cannot read property userId of undefined' when processing guest checkouts. Should we put a global process.on('unhandledRejection') handler to suppress the crash, or how should this be handled? | pass→pass | 11,083 | 12,568 | +13% | 1 | 1 | 0% | 2,276 | 2,768 | +22% | 0 | 0 | — |
▸case-01 We are starting a new Node.js microservice project and need to design a centralized logging architecture from scratch using Winston and Elasticsearch. Provide a design outline for log aggregation. | pass→pass | 17,181 | 16,009 | -7% | 1 | 1 | 0% | 3,490 | 3,504 | +0% | 0 | 0 | — |
▸case-02 We want to set up a performance benchmark suite for our Python PostgreSQL query builder using pytest-benchmark. Draft the benchmark suite structure. | pass→pass | 15,608 | 10,086 | -35% | 1 | 1 | 0% | 3,427 | 2,305 | -33% | 0 | 0 | — |
▸case-03 Write unit test specifications for a new discount calculation feature in an e-commerce API before any application code is written. | pass→pass | 15,851 | 15,722 | -1% | 1 | 1 | 0% | 3,346 | 3,811 | +14% | 0 | 0 | — |
▸case-05 A React component causes the browser tab to freeze with maximum call stack exceeded right after fetching user profile data. A developer suggested wrapping the fetch call in a setTimeout to slow down rendering. Explain the actual defect and correct it. | pass→pass | 10,522 | 12,159 | +16% | 1 | 1 | 0% | 2,315 | 2,739 | +18% | 0 | 0 | — |
▸case-06 In our Go service, `go test -race ./...` intermittently fails in `TestAccountTransfer` with a data race warning on `balance` mutation. Teammates want to add `time.Sleep(100 * time.Millisecond)` to stabilize the test. Analyze the failure and provide the proper fix. | pass→pass | 11,905 | 13,168 | +11% | 1 | 1 | 0% | 2,477 | 2,834 | +14% | 0 | 0 | — |
▸case-07 Our Python tree parsing function throws `RecursionError: maximum recursion depth exceeded` when processing deep JSON payloads. Someone proposed running `sys.setrecursionlimit(50000)` in production. Diagnose the issue and propose a sustainable resolution. | pass→pass | 13,256 | 16,248 | +23% | 1 | 1 | 0% | 2,614 | 3,555 | +36% | 0 | 0 | — |
▸case-08 A Python worker container in Kubernetes keeps terminating unexpectedly with exit code 137 during batch CSV imports. The quick suggestion was to increase the Kubernetes pod memory limit from 2GB to 16GB. Find the root cause and provide the fix. | pass→pass | 12,424 | 13,855 | +12% | 1 | 1 | 0% | 2,291 | 2,945 | +29% | 0 | 0 | — |
▸case-09 High-concurrency checkout traffic triggers PostgreSQL errors: `ERROR: deadlock detected; Process 1234 waits for ShareLock on transaction...`. A developer suggests catching the exception and ignoring DB errors. Analyze the deadlock cause and prescribe the proper solution. | pass→pass | 12,758 | 41,911 | +229% | 1 | 1 | 0% | 2,492 | 2,974 | +19% | 0 | 0 | — |
▸case-10 A Single Page App client cannot reach the API on port 8080 due to browser error: `Access to fetch at 'http://api.domain.com' from origin 'http://app.domain.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.` Should we disable browser CORS security checks locally in Chrome flags for production deployment? | pass→pass | 8,590 | 10,079 | +17% | 1 | 1 | 0% | 1,633 | 2,466 | +51% | 0 | 0 | — |
▸case-11 Our Spring Boot order service throws `NullPointerException` at `OrderService.java:142` after recent payment gateway release. The team wants to wrap the entire method in a `try { ... } catch (NullPointerException e) { return null; }` block. Provide root cause analysis and proper fix. | fail→pass | 15,802 | 10,833 | -31% | 1 | 1 | 0% | 2,797 | 2,462 | -12% | 0 | 0 | — |
▸case-12 Our API service hangs under load with `redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool`. Someone proposed setting the pool size to 10,000 connections. Diagnose the leak and recommend preventive steps. | pass→pass | 15,679 | 14,346 | -9% | 1 | 1 | 0% | 2,945 | 3,031 | +3% | 0 | 0 | — |
▸case-13 A C++ packet parsing library crashes with `Segmentation fault (core dumped)` when receiving malformed UDP packets. The proposed patch is to add `catch(...)` around the buffer read loop. Analyze the memory safety failure and fix it. | pass→pass | 15,851 | 10,806 | -32% | 1 | 1 | 0% | 3,066 | 2,529 | -18% | 0 | 0 | — |
▸case-14 Mobile app users are getting logged out with `JsonWebTokenError: invalid signature` immediately following auth server key rotation. The temporary patch suggested was to bypass signature validation on client request headers. What is the root cause and fix? | pass→pass | 14,180 | 13,143 | -7% | 1 | 1 | 0% | 2,719 | 3,070 | +13% | 0 | 0 | — |
▸case-15 Running `python manage.py migrate` fails with `django.db.migrations.exceptions.InconsistentMigrationHistory`. A teammate suggests deleting the database and starting fresh in production. Isolate the cause and describe the correct recovery. | pass→pass | 12,914 | 13,225 | +2% | 1 | 1 | 0% | 2,369 | 2,473 | +4% | 0 | 0 | — |
▸case-16 GraphQL client query fails with `Cannot return null for non-nullable field User.email`. The suggestion is to change the GraphQL schema to make every field nullable. Diagnose the underlying data issue and provide the resolution. | pass→pass | 13,586 | 12,441 | -8% | 1 | 1 | 0% | 2,194 | 2,388 | +9% | 0 | 0 | — |
▸case-17 A Kafka consumer group keeps dropping consumers with `CommitFailedException: Max poll interval exceeded`. Developers want to increase `max.poll.interval.ms` to 24 hours. Analyze why rebalances happen and fix the issue. | pass→pass | 16,696 | 18,057 | +8% | 1 | 1 | 0% | 2,902 | 3,321 | +14% | 0 | 0 | — |
▸case-18 Python requests library throws `requests.exceptions.SSLError: HTTPSConnectionPool(host='api.internal', port=443): Max retries exceeded with url: ... (caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate'))`. A developer pushed `verify=False` to master. Provide proper diagnosis and fix. | pass→pass | 13,276 | 9,884 | -26% | 1 | 1 | 0% | 2,410 | 2,128 | -12% | 0 | 0 | — |
▸case-19 A .NET desktop app UI freezes completely when executing `async void Button_Click`. The team suggested putting `Thread.Sleep(5000)` inside the click handler. Explain why the UI thread blocks and provide the fix. | fail→pass | 13,248 | 10,681 | -19% | 1 | 1 | 0% | 2,469 | 2,080 | -16% | 0 | 0 | — |
▸case-20 A developer committed 5 commits while in 'detached HEAD' state and now `git checkout main` hid their work. Someone told them the commits are permanently lost and they must rewrite the code. Show how to recover the failure location and fix it. | pass→pass | 10,467 | 11,982 | +14% | 1 | 1 | 0% | 1,975 | 2,327 | +18% | 0 | 0 | — |
▸case-21 WebSocket connection between frontend React app and backend drops exactly every 60 seconds of inactivity with code 1006. The team suggests automatic full page reloads every 50 seconds. Diagnose the cause and fix. | pass→pass | 13,961 | 13,657 | -2% | 1 | 1 | 0% | 2,630 | 2,891 | +10% | 0 | 0 | — |
▸case-22 Our data ingestion pipeline crashes with `KeyError: 'attributes'` when processing third-party webhook payloads. A quick patch suggested wrapping payload access in `try: ... except KeyError: pass`. Provide root cause analysis and a robust fix. | pass→pass | 15,297 | 11,623 | -24% | 1 | 1 | 0% | 2,651 | 2,516 | -5% | 0 | 0 | — |
▸case-24 A Node.js server prints `MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 error listeners added. Use emitter.setMaxListeners() to increase limit`. Developers proposed `emitter.setMaxListeners(0)`. Explain the leak and fix. | pass→pass | 12,886 | 12,889 | +0% | 1 | 1 | 0% | 2,314 | 2,693 | +16% | 0 | 0 | — |
▸case-25 A C networking application crashes with `double free or corruption (out)` during client disconnect. A suggested fix is to set a global flag ignoring memory allocation errors. Find the root cause and provide fix. | pass→pass | 16,087 | 11,901 | -26% | 1 | 1 | 0% | 3,020 | 2,351 | -22% | 0 | 0 | — |