The basics, written so you can check them. Every claim a lesson makes is either a definition or an example you can run here, on real infrastructure, and see the output of.
The language every backend job assumes you already know, from SELECT and joins through NULL logic, window functions and constraints to transactions and indexes.
Types on top of JavaScript, from annotations to the narrowing that makes the compiler useful rather than noisy.
The language every frontend and Node job assumes you already know — values, functions, this, and the async model that trips almost everyone up once.
The basics behind the syntax — mutability, scope, comprehensions, and the object model — not just how to write a for loop.
Core types, equals and hashCode, collections, generics, streams, the JVM heap and concurrency — the Java an interview actually probes, with the mistakes almost everyone makes once.
Value types against reference types, collections, interfaces and LINQ — the fundamentals behind every .NET job posting.
The ASP.NET Core and EF Core mechanics backend interviews probe, from the middleware pipeline and DI lifetimes to change tracking, N+1, caching and JWTs.
Beans, auto-configuration, MVC, validation, Data JPA, transactions, N+1, caching, security, actuator and test slices, each mechanism modelled as plain Java you can run.
The mental model behind React 19 — what a render is, why state is a snapshot, when effects run, and the reconciliation, memo and race-condition questions interviews keep returning to.
Past the basics into what PostgreSQL interviews actually probe — NULL logic, LATERAL, recursive CTEs, window frames, JSONB, UPSERT, indexes, EXPLAIN, MVCC and locking.
MySQL 8.4 as interviewers probe it: InnoDB's clustered key, collations, strict mode, ONLY_FULL_GROUP_BY, JSON, upserts, EXPLAIN, REPEATABLE READ and the locks behind deadlocks.
T-SQL as SQL Server shops actually write it — indexes, seeks and plans, window functions, MERGE, procedures, isolation and deadlocks — with every claim run on SQL Server 2022.
Resources, methods, status codes, errors, pagination, caching, versioning and auth — the HTTP decisions every backend interview probes, each one modelled as code you can run.