.NET

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.

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In this course

Hosting and the request pipelineWhat WebApplication builds at startup, and why middleware nests like an onion instead of running as a queue.9 min
Middleware order and short-circuitingUse, Run, Map and UseWhen, what happens when a component does not call next, and why the exception handler goes first.9 min
Dependency injection and service lifetimesTransient, scoped and singleton, what a scope is in ASP.NET Core, and who disposes what the container creates.9 min
Captive dependenciesA singleton that takes a scoped service keeps the first one forever. How it happens, how the container catches it, and the fixes.8 min
Configuration and the options patternWhere a configuration value comes from, which source wins, and the difference between IOptions, IOptionsSnapshot and IOptionsMonitor.10 min
Minimal APIs, controllers, routing and bindingThe same endpoint written both ways, what a route constraint really does, and how a handler parameter's value source is chosen.10 min
Model validation and problem detailsData annotations, the attributes that quietly pass on null, IValidatableObject, and the 400 response clients actually receive.10 min
Logging, categories and message templatesILogger categories and levels, how the most specific filter wins, and why a message template is not an interpolated string.9 min
Async handlers and cancellationWhy blocking on a Task starves the server, how RequestAborted reaches your code, and how to tell a client disconnect from a timeout.9 min
EF Core change trackingEntity states, snapshot change detection, identity resolution, and exactly which SQL SaveChanges sends.10 min
Loading related data and the N+1 problemLazy, eager and explicit loading, how N+1 happens, and the cartesian explosion that a naive fix walks into.10 min
EF Core migrationsWhat a migration is diffed against, how the history table decides what runs, and how to ship schema changes without downtime.9 min
Caching in ASP.NET CoreIn-memory versus distributed caches, absolute versus sliding expiration, cache stampedes, and the cache key that leaks data.10 min
Background services and queuesIHostedService and BackgroundService, why work before the first await delays startup, and queueing work with a bounded Channel.10 min
JWT authentication and authorizationWhat is inside a JWT, how the API validates one, the clock skew nobody remembers, and the line between a 401 and a 403.11 min
Unit testing with fakesStubs, fakes, spies and mocks, injecting TimeProvider instead of reading the clock, and where EF Core's in-memory provider misleads you.10 min