Interview Prep

Real questions for real interviews. C#, Python, Go. Junior → System Design.

Quiz me →

C# / .NET

Junior

What is the difference between value types and reference types in C#?
Concepts Very frequent C# memory types
What is the difference between an interface and an abstract class in C#?
Concepts Very frequent C# interface abstract class
What is boxing and unboxing in C#, and why is it a performance concern?
Concepts Frequent C# boxing unboxing

Mid-level

How does async/await work under the hood in C#? What is the state machine?
Concepts Very frequent C# async await
What is the difference between IEnumerable<T> and IQueryable<T>?
Concepts Frequent C# LINQ EF Core
What is dependency injection (DI) and how does ASP.NET Core's built-in container work?
Concepts Very frequent C# dependency injection IoC
Explain delegates, Func, Action, and events in C# — when do you use each?
Concepts Very frequent C# delegates Func
What is middleware in ASP.NET Core and how is the pipeline composed?
Concepts Frequent C# ASP.NET Core middleware

Senior

Explain the .NET Garbage Collector — what are the generations and what triggers a Gen 2 collection?
Concepts Frequent C# .NET GC
What are Span<T> and Memory<T> in C#, and when should you use them?
Concepts Frequent C# Span Memory

System Design

Explain the CAP theorem and how it applies to distributed .NET services
Concepts Frequent C# CAP theorem distributed systems

Python

Junior

What is the difference between a list and a tuple in Python, and when would you use each?
Concepts Very frequent Python list tuple
What are *args and **kwargs in Python, and when do you use them?
Concepts Very frequent Python *args **kwargs
What is a list comprehension in Python, and how does it differ from a generator expression?
Concepts Very frequent Python list comprehension generator

Mid-level

What is the GIL in CPython and when does it limit performance?
Concepts Frequent Python GIL concurrency
What are context managers in Python and how do you implement one with __enter__ and __exit__?
Concepts Very frequent Python context manager __enter__

Senior

How does Python's asyncio event loop work, and when do you prefer it over threading?
Concepts Frequent Python asyncio event loop
What are Python descriptors and how do they underpin properties and ORM fields?
Concepts Frequent Python descriptors __get__

System Design

When do you choose SQL vs NoSQL, and what are the consistency trade-offs?
Concepts Very frequent Python SQL NoSQL

Go

Junior

What is the difference between a goroutine and an OS thread?
Concepts Very frequent Go goroutines concurrency
How do interfaces work in Go? Explain duck typing and implicit satisfaction
Concepts Very frequent Go interfaces duck typing
What are slices in Go, and how do they differ from arrays?
Concepts Very frequent Go slices arrays

Mid-level

Explain Go's error handling pattern. When should you use panic and recover?
Concepts Frequent Go error handling panic
What is the context package in Go and how do you use it for cancellation and deadlines?
Concepts Very frequent Go context cancellation
Explain the select statement in Go — how does it multiplex channels?
Concepts Frequent Go select channels

Senior

Explain Go's memory model and what happens-before guarantees mean in practice
Concepts Frequent Go memory model happens-before

System Design

What is consistent hashing and when would you use it in a Go distributed system?
Concepts Frequent Go consistent hashing distributed systems