Practice

Hands-on problems with a real editor and real execution. Run your answer, look at what came back, then submit it to find out whether it is right.

Backend

Queries, aggregation pipelines and data modelling

Event loop, streams, async patterns and performance

Joins, window functions and query planning

Data structures, caching strategies and expiry

Images, layers, networking and compose

Data structures, algorithms and complexity

OOP, SOLID and design patterns applied

Scaling, storage choices and trade-offs