Why should you care?

One giant app is simple at first. But when traffic spikes or ten developers edit the same codebase, deploys get scary. Small services let one team ship Payment without touching Product catalog.

See it live — copy this example

Create a Web API project (dotnet new webapi), paste the code, then run dotnet run.

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.MapPost("/orders", (CreateOrderRequest req) =>
{
    var orderId = Guid.NewGuid();
    return Results.Created($"/orders/{orderId}",
        new { orderId, req.ProductId, Status = "Created" });
});

app.Run();

record CreateOrderRequest(int ProductId, int Quantity);

Run Example »

Edit the code and click Run — like W3Schools Try it Yourself.

What happened?

• This is one microservice — Order only.
• It creates an order and returns an id.
• It does not charge a card or send email.
• Those are other services you will build later.

Try it yourself

1. Install .NET 8+ SDK from https://dotnet.microsoft.com
2. Run: dotnet new webapi -n ShopNest.Order.Api
3. Replace Program.cs with the lesson example (minimal API style).
4. Change a string or route in the example and save — watch Swagger or the RabbitMQ Management UI update.
5. Break the code on purpose (remove a semicolon), read the error message, then fix it.

Remember

A microservice is a small ASP.NET Core app with one business job. Each service should own its own data. Start with one working API before splitting further.

Real-world: Flipkart checkout on sale day

During Big Billion Day, order traffic jumps 50×. With microservices, Order and Payment scale separately. Product catalog does not need 40 extra servers just because checkout is busy.

Outcome: Order saves fast and returns. Payment and Inventory react to the event — shoppers see "confirming payment" instead of a frozen spinner.