.NET and C# interview questions

I create a Meter and counters or histograms for business events.

Build the provider with validate-on-build and validate-scopes enabled in Development.

I use Microsoft.FeatureManagement or a remote flag service with filters by user and environment.

HttpOnly, Secure, SameSite, short lifetimes, and sliding refresh with care.

I batch with AddRange, raise MaxBatchSize, or use bulk extensions for millions of rows.

I split by bounded context folders or projects with clear interfaces, one deployable host.

gRPC shines for internal service-to-service with protobuf and HTTP/2 streaming.

I add IsDeleted and a global query filter, plus careful unique indexes that include the flag.

For huge loads I use bulk extensions, COPY-like tools, or raw SQL, not SaveChanges per row.

I use built-in rate limiter middleware with fixed or sliding windows per IP or user.

I publish multiple validation keys and phase old ones out after token lifetime.

Sync-over-async, blocking calls, and too few threads show as delayed requests with low CPU.

WebApplicationFactory hosts the app in memory with a test server.

I store processed message ids or use natural idempotency keys before side effects.

URL versioning or header versioning with Asp.Versioning packages.

Only redirect to local URLs with Url.IsLocalUrl or an allowlist.

Span views memory without allocating for slicing and parsing.

AsSplitQuery avoids cartesian explosion from multiple includes.

Authorize hubs and methods, validate users on connect, and avoid trusting client payloads.

I add tenant id filters globally and set tenant from the request.