5–8 years · Senior — Python · Django / Flask / FastAPI · REST APIs · SQL · Celery · Testing
Checks the API response for proper success messages; verifies database transactions for consistency; inspects the caching layer for stale data; reviews logs for errors or exceptions during updates; identifies if there’s a race condition affecting the updates.
You find out that the updates are being cached incorrectly. What changes do you make to ensure data consistency?
Gathers essential requirements from stakeholders to prioritise functionalities; evaluates existing services for potential reuse to save time; designs a minimal viable product (MVP) focusing on core functionality; discusses trade-offs with the team regarding scalability and future enhancements; sets a timeline for iterative improvements post-launch.
Once the service is deployed, you learn it isn't scaling as expected. What steps do you take to address this?
Identifies the specific incident and its impact; outlines the immediate steps taken to diagnose the issue; details the resolution process and communication with stakeholders; mentions any long-term changes implemented to prevent recurrence; reflects on lessons learned from the incident.
What would you do differently next time?
Checks Celery worker logs for errors or long-running tasks; looks at the task queue length and identifies if tasks are stuck; profiles the task to find bottlenecks; considers splitting the task into smaller, more manageable chunks; evaluates worker concurrency settings.
What factors could lead to tasks being stuck in the queue?
Profiles the API endpoint to identify slow components; checks database queries for efficiency and index usage; implements caching for frequent requests; considers rate limiting to manage load; monitors system metrics for further insights.
After optimisations, the API still underperforms. What do you explore next?
Identifies slow tests by profiling test execution; considers parallelising test execution with pytest-xdist; checks for unnecessary I/O operations during tests; removes redundant tests or merges similar ones; evaluates the use of mocking to reduce dependencies on external services.
How do you determine which tests should be run in parallel versus sequentially?
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