Why should you care?

Catalog changes constantly (sales, new SKUs). Isolating Product lets merchandising deploy without regression-testing Payment.

See it live — copy this example

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

app.MapGet("/products", async (ProductDbContext db) =>
    Results.Ok(await db.Products.AsNoTracking().ToListAsync()));

app.MapGet("/products/{id:int}", async (int id, ProductDbContext db) =>
{
    var p = await db.Products.FindAsync(id);
    return p is null ? Results.NotFound() : Results.Ok(p);
});

Run Example »

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

What happened?

• AsNoTracking on list queries is faster for read-heavy catalog.
• Order service will store productId and price snapshot when order is placed.

Try it yourself

1. Create Product.Api with Product entity (Id, Name, Price, Description).
2. Seed five products in migration or POST loop.
3. Test list and get-by-id in Swagger.
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

Product service = catalog CRUD. Read-heavy — optimize reads later with Redis (lesson 68). Order stores snapshot of price at purchase time.

Real-world: Big Billion Day pricing

Prices flash every hour. Product service deploys price rules; CDN caches GET /products with short TTL.

Outcome: Checkout reads price from order line snapshot — not live catalog — so totals do not change after click.