Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About EY hiring for .NET Full Stack roles
EY is one of the Big Four professional services networks, offering assurance, tax, strategy and transactions, and consulting services. In India, EY GDS and EY member firms support global clients with technology consulting, data analytics, cybersecurity and risk work. It hires for analyst and consultant roles in data analytics, BI, testing, ERP and risk.
For .NET Full Stack roles, this EY practice set focuses most on Angular and React Front End (6), ASP.NET Core Web API (6), Entity Framework Core (4), Async Programming and Multithreading (4). It has 5 easy, 22 medium, 3 hard questions, so you can start easy and work up to the harder ones.
Company type
Consulting
Headquarters
London, United Kingdom
Main India offices
Bengaluru, Kolkata, Gurugram, Hyderabad, Kochi
EY .NET Full Stack interview process
Online assessment (aptitude + technical)
Technical interview
Managerial or case round
Partner or HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
Solved for EYStart practicing
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01
How do you manage application state in Angular and React apps?
Start simple: local component state, then share through a parent or a service. In Angular, a service holding signals covers most needs, and NgRx or NgRx SignalStore suits large apps with complex flows. In React, Context works for low-frequency data like theme or user, Redux Toolkit or Zustand for complex client state, and TanStack Query for server data with caching. Keep server data and UI state separate.
02
Sort a list of students by marks descending, then by name ascending.
var ranked = students
.OrderByDescending(s => s.Marks)
.ThenBy(s => s.Name)
.ToList();
// in-place alternative with a comparison
students.Sort((a, b) =>
b.Marks != a.Marks ? b.Marks.CompareTo(a.Marks)
: string.Compare(a.Name, b.Name, StringComparison.Ordinal));
OrderBy is stable and returns a new sequence; List.Sort sorts in place and is not stable.
03
Implement global exception handling that returns ProblemDetails.
Versioning lets you change contracts without breaking existing clients such as mobile apps that users have not updated. Common approaches are URL segments (/api/v1/orders), query strings (?api-version=2.0) and headers. The Asp.Versioning library supports all of them and integrates with OpenAPI docs. URL versioning is the most visible and cache-friendly. Keep old versions running for a published period, then deprecate them with headers.
06
What is the difference between an RxJS Observable and a Promise?
A Promise represents a single future value, starts immediately and cannot be cancelled. An Observable can emit many values over time, is lazy until subscribed, and can be cancelled by unsubscribing. RxJS operators like map, debounceTime, switchMap and retry make it powerful for streams such as search boxes or WebSocket data. Angular's HttpClient returns Observables; use the async pipe or toSignal to avoid manual unsubscribe.
07
An admin page renders 20,000 rows in a table and the browser freezes. How do you fix it?
Do not send or render everything at once. Add server-side paging, sorting and filtering in the ASP.NET Core API so the page loads perhaps 50 rows at a time. If users truly need to scroll a long list, use virtual scrolling, such as Angular CDK virtual scroll or TanStack Virtual in React, so only visible rows exist in the DOM. Also use trackBy or keys, and debounce search inputs.
08
Your team debates wrapping EF Core in a generic repository. What is your view?
DbContext already implements Repository and Unit of Work, so a thin generic repository with GetAll and Add often adds code while hiding useful features like Include, projections and AsNoTracking. I prefer either using DbContext directly in services, or specific repositories with meaningful methods like GetOverdueInvoicesAsync that encapsulate queries. For tests, use the SQLite in-memory provider or Testcontainers rather than mocking DbSet.
09
Explain a technical trade-off you had to justify to a manager or client.
On a reporting module (Situation) the manager wanted everything in EF Core for consistency, but one report was too slow. My task was to recommend a fix without derailing the plan. I measured the EF query against a Dapper version with a hand-tuned SQL query, showed the 8x difference and explained that we would use Dapper only for that read path. Result: the manager approved, the report loaded in under a second, and the rest stayed in EF Core.
10
Demonstrate a race condition on a counter and fix it.
int count = 0;
Parallel.For(0, 100_000, _ => count++);
Console.WriteLine(count); // often less than 100000
int safe = 0;
Parallel.For(0, 100_000, _ => Interlocked.Increment(ref safe));
Console.WriteLine(safe); // always 100000
count++ is a read, add and write, so two threads can read the same value and lose an update. Interlocked performs the increment atomically without a full lock.
11
What is the difference between const, readonly and static readonly?
const is a compile-time constant, implicitly static, and its value is copied into calling assemblies, so changing it requires recompiling them. readonly fields are set at declaration or in the constructor and can differ per instance. static readonly is set once per type at runtime, so it can hold values like DateTime.Now or a new object. Use const only for values that will never change, such as Math.PI.
12
Under load, an API's response time jumps to many seconds while CPU stays low. Thread count keeps rising. What is likely happening?
This pattern points to thread pool starvation. Some code is blocking threads with .Result, .Wait(), Thread.Sleep or synchronous I/O, so pool threads are stuck waiting and the pool injects new threads slowly. Confirm with dotnet-counters, watching thread pool queue length and thread count, and a dump showing many threads blocked in Wait. Fix by making the call chain fully async; raising minimum threads is only a temporary patch.
13
A large Angular dashboard becomes sluggish because change detection runs constantly. How do OnPush and zoneless mode help?
Traditionally Zone.js patched browser events and timers, and after each one Angular checked every component for changes, top to bottom. OnPush makes a component re-check only when its inputs change by reference, an event occurs inside it, an async pipe emits or a signal it reads changes, which saves work in big screens. Zoneless mode removes Zone.js entirely and relies on signals and explicit triggers, reducing bundle size and improving performance.
14
A teammate created a deep inheritance chain Employee > Manager > SeniorManager > RegionalHead to add features. What would you suggest?
Deep hierarchies are fragile: a change in a base class ripples into every child, and behaviours that do not fit the tree get duplicated. I would suggest composition over inheritance. Keep a single Employee entity and give it composed parts such as a Role, an ApprovalPolicy and a list of Permissions, injected as interfaces. New behaviour then means a new policy class, not a new subclass, which is easier to test.
Authorization filters run first and can block a request. Resource filters run before model binding, useful for caching. Action filters run before and after an action, for logging or validation. Exception filters handle errors thrown by actions. Result filters run around the result execution, for example to add headers. Filters apply globally, per controller or per action. Unlike middleware, they can access MVC details like action arguments.
16
Tell me about a disagreement with the front-end team over an API contract and how you resolved it.
On a dashboard feature (Situation) the React team wanted one endpoint returning everything, while I worried about payload size. My task was to agree a design quickly. I set up a short call, we listed exact screen needs, and I proposed one aggregated endpoint with paging and optional fields. We wrote the OpenAPI spec together. Result: payload dropped by half, the UI got one call, and the spec became our template for later features.
17
Write a BackgroundService that cleans expired OTPs every 5 minutes.
public class OtpCleanupService(IServiceScopeFactory scopes) : BackgroundService
{
protected override async Task ExecuteAsync(CancellationToken ct)
{
using var timer = new PeriodicTimer(TimeSpan.FromMinutes(5));
while (await timer.WaitForNextTickAsync(ct))
{
using var scope = scopes.CreateScope();
var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
await db.Otps.Where(o => o.ExpiresAt < DateTime.UtcNow).ExecuteDeleteAsync(ct);
}
}
}
// builder.Services.AddHostedService<OtpCleanupService>();
A scope is created because DbContext is scoped while hosted services are singletons.
18
How do you keep up with new .NET and EF Core releases?
Microsoft ships a major .NET version every November, so I plan for it. I read the official What's New pages and the .NET blog, watch .NET Conf sessions, and try new features in a small side project before suggesting them at work. For example, when ExecuteUpdate arrived, I tested it on a sample and then proposed replacing a slow loop in our cleanup job, which cut its runtime significantly.
19
How do model binding and validation work in ASP.NET Core Web API?
Model binding maps request data into action parameters from the route, query string, headers or body, using [FromRoute], [FromQuery] and [FromBody]. Validation uses data annotations like [Required], [StringLength] and [Range] on DTOs. With [ApiController], invalid models automatically return 400 Bad Request with ProblemDetails listing the errors, so you do not need to check ModelState manually. FluentValidation is popular for complex rules.
20
You must resize 10,000 images and also call an external API for 10,000 records. Which approach do you use for each task?
Parallel.ForEach is for CPU-bound work, such as resizing thousands of images, where splitting work across cores speeds things up. async/await is for I/O-bound work, where you mostly wait on networks or disks. Using Parallel.ForEach for HTTP calls wastes threads while they wait. For many concurrent I/O operations with a limit, use Parallel.ForEachAsync with MaxDegreeOfParallelism, available since .NET 6.
21
Tell me about a time you refactored messy code that others depended on.
In my last project (Situation) an invoice module had one 900-line class with duplicated GST logic. My task was to add a new tax rule without breaking billing. I first wrote unit tests around current behaviour, then extracted tax rules into strategy classes and moved data access into a repository, merging in small pull requests. Result: the new rule took one day, and bugs in that module dropped noticeably the next quarter.
22
What is the difference between == and Equals() in C#?
For reference types, == by default checks reference equality, meaning both variables point to the same object, while Equals can be overridden to compare content. String overrides both, so == compares text. For value types, Equals compares field values. Records generate value-based equality automatically. When you override Equals, also override GetHashCode so objects behave correctly in dictionaries and hash sets.
Single Responsibility: a class has one reason to change. Open/Closed: extend behaviour without editing existing code. Liskov Substitution: derived types must work wherever the base type is expected. Interface Segregation: prefer small, focused interfaces over one fat interface. Dependency Inversion: depend on abstractions, not concrete classes. In ASP.NET Core, injecting IEmailSender into a controller instead of creating SmtpClient directly applies dependency inversion.
24
A job matches 2 lakh uploaded records against 2 lakh existing IDs using list.Where(x => existingIds.Contains(x.Id)) and takes minutes. What is wrong?
existingIds is a List, so Contains is O(n) and the whole operation becomes O(n x m), around 40 billion comparisons. Convert the IDs to a HashSet<int> first, making each lookup O(1) and the job run in milliseconds. If you also need associated data, build a Dictionary keyed by ID. Always check data structure complexity before parallelising or adding hardware.
25
A developer runs two EF Core queries in parallel with Task.WhenAll on the same DbContext and gets an InvalidOperationException. Why?
DbContext is not thread-safe and supports only one active operation at a time, so starting a second query before the first finishes throws 'A second operation was started on this context instance'. Either await the queries one after another, or create a separate context for each parallel query using IDbContextFactory. Usually sequential queries are fine; parallelism only helps when the queries are slow and independent.
26
When would you choose an array, a List<T> or a LinkedList<T>?
An array has a fixed size and fastest index access, good when the count is known. List<T> wraps a resizable array, with O(1) index access and amortised O(1) add at the end, and is the default choice for most code. LinkedList<T> gives O(1) insert and remove at a known node but O(n) access by index and poor cache locality, so it is rarely the better option in practice.
27
Show an example of the Dependency Inversion Principle in C#.
public interface INotifier { Task SendAsync(string to, string msg); }
public class SmsNotifier : INotifier
{
public Task SendAsync(string to, string msg) => Task.CompletedTask; // call SMS API
}
public class OrderService(INotifier notifier)
{
public Task ConfirmAsync(Order o) => notifier.SendAsync(o.Phone, "Order placed");
}
// Program.cs
builder.Services.AddScoped<INotifier, SmsNotifier>();
OrderService depends on the abstraction, so you can swap to email or a mock without changing it.
28
You are designing a type to hold a 2D point used millions of times in a calculation. Struct or class?
A struct is a good fit because the point is small, logically a single value and created in huge numbers. Structs avoid heap allocation and GC pressure when stored in arrays or locals. Make it a readonly struct so it is immutable and avoids defensive copies. Choose a class instead if the type is large, needs inheritance, or is frequently boxed through interfaces, since copying and boxing remove the benefit.
29
What is the difference between props and state in React?
Props are inputs passed from a parent component to a child, like function arguments, and the child must not modify them. State is data owned and managed inside a component with useState or useReducer, and changing it re-renders the component. For example, a ProductCard receives product details as props, while a Cart component keeps the quantity in state. Shared state is lifted up to a common parent or moved into a store.
30
Which HTTP status codes and methods should a REST API use, and what is the difference between PUT and PATCH?
GET reads, POST creates, PUT replaces, PATCH partially updates and DELETE removes. Return 200 OK for success with a body, 201 Created with a Location header after POST, 204 No Content after delete, 400 for invalid input, 401 unauthenticated, 403 forbidden, 404 not found, 409 conflict and 500 for server errors. PUT sends the full resource and is idempotent; PATCH sends only changed fields.
Tips to crack the EY .NET Full Stack interview
Practise explaining a data project in business terms, focusing on the problem, approach and recommendation for the client.
Revise Excel, SQL and Power BI, which appear frequently in EY analytics and consulting job descriptions.
Read about EY's service lines and its focus on technology, AI and sustainability consulting for fit questions.
Keep a one-minute story ready for every project on your CV: problem, your part, tools, result.
Practise the hard questions on this page aloud; EY interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the EY .NET Full Stack interview?
Candidates usually go through 4 stages: Online assessment (aptitude + technical); Technical interview; Managerial or case round; Partner or HR round. The exact rounds change with the role, team, location and your experience, so confirm the process with the recruiter.
Which topics should I prepare for the EY .NET Full Stack interview?
This practice set leans on Angular and React Front End (6), ASP.NET Core Web API (6), Entity Framework Core (4), Async Programming and Multithreading (4). Revise those first, then practise explaining one or two of your own projects end to end, because most EY interviewers ask you to walk through real work.
Are these the exact questions asked at EY?
No. These are curated practice questions that match the skills and difficulty usually tested in consulting interviews like EY's. They are not a leaked or verified list of past questions.
Where does EY hire .NET Full Stack professionals in India?
EY has large teams in Bengaluru, Kolkata, Gurugram, Hyderabad, Kochi. Openings and locations change often, so check the EY careers page and filter by city and experience.