Phase 6 — Asynchronous Programming and Multithreading

Threads, tasks, synchronisation primitives, advanced async patterns and the concurrency problems seen in production .NET systems.

41. Which blocking calls cause problems in ASP.NET Core, how do you find them, and what should replace them?

    Synchronous I/O and AllowSynchronousIO, EF Core sync APIs, HttpClient.Send, Thread.Sleep, long locks, heavy synchronous logging; detection with analysers, traces and load tests.

    Mid-Level CodeReview Concurrency Production Problems · 🔗 3 follow-ups · 🛠 1 real-world
42. What is unbounded concurrency, why does it take systems down, and how do you put limits in place in .NET?

    Unbounded Task.WhenAll, Task.Run per request, unlimited queues and connections; Little's law; limits with SemaphoreSlim, Parallel.ForEachAsync, bounded channels, rate limiting middleware and bulkheads.

    Senior Architecture Concurrency Production Problems · 🔗 3 follow-ups · 🛠 1 real-world
43. What is backpressure, and how do you implement it across a .NET system, from in-process queues to message brokers and HTTP APIs?

    Backpressure strategies (block, buffer, drop, reject), bounded channels, pull-based streams, broker prefetch and concurrency settings, HTTP 429/503 with Retry-After, and metrics.

    Staff / Architect SystemDesign Concurrency Production Problems · 🔗 3 follow-ups · 🛠 1 real-world