Why should you care?

You care about this when basic CRUD and RabbitMQ are working and you need reliable events, auth, or gradual migration from a legacy monolith.

See it live — copy this example

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

builder.Services.AddCors(o => o.AddPolicy("shopnest", p =>
    p.WithOrigins("https://app.shopnest.com").AllowAnyHeader().AllowAnyMethod()));

Run Example »

This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.

What happened?

• The example shows CORS in Microservices wired into User Service.
• Read each line, run it locally, then change one setting and observe what breaks or improves.
• That is how teams learn in production too — small experiments, not big bang rewrites.

Try it yourself

1. Open or create the ShopNest project area for User Service.
2. Apply the CORS in Microservices pattern from the lesson example.
3. Run dotnet build && dotnet run (or docker compose up when the lesson uses containers).
4. Change a string or number in the example and run again — predict the output first.
5. Break the code on purpose (remove a semicolon), read the compiler error, then fix it.

Remember

CORS in Microservices connects to User Service in ShopNest Cloud-Native. Practice by editing the example yourself — do not only read. Move on when you can explain this topic in your own words without looking.

Real-world: HDFC-style fund transfer

Transfer, ledger, fraud check, and SMS run as separate services with idempotency keys. Saga compensates if fraud blocks after debit.

Outcome: Salary-day load handled without duplicate debits or shared-database locks.