Performance

I once spent the better part of a week chasing a bug that only appeared in our staging environment under heavy load. A user from one organization would suddenly see data belonging to another. We’d check the logs, query the database directly, and everything looked fine. It was a ghost.

The culprit? A single line change someone made to “optimize” our database access: switching AddDbContext to AddDbContextPool. That optimization introduced a state-sharing bug that was nearly impossible to reproduce locally.

DbContext pooling in EF Core is one of those features that promises a big performance win, but it comes with a massive, sneaky gotcha. Let’s break down what it is, where it shines, and how to use it without shooting yourself in the foot.

So, what’s DbContext pooling anyway?

Normally, when you register your DbContext in an ASP.NET Core app, you use a scoped lifetime. This is the default and the safest option.

// The standard, safe way: A new instance for every HTTP request.
services.AddDbContext<AppDbContext>(options => 
    options.UseSqlServer(connectionString));

This means for every single web request, the dependency injection container creates a brand-new DbContext instance. When the request is over, that instance is thrown away. Simple, clean, and isolated.

DbContext pooling changes the game. Instead of creating a new instance every time, it keeps a “pool” of DbContext instances ready to go.

// The high-performance way: …

I’ll never forget the first time I got called at midnight for a performance issue that was my fault. A dashboard in our SaaS app was timing out, and customers were angry. After hours of digging, the culprit was a monster LINQ query generated by Entity Framework Core. It was trying to be clever, but the generated SQL was a performance disaster.

We rewrote that one query using raw SQL with Dapper, and boom: the endpoint went from taking 15 seconds to under 200 milliseconds.

That experience taught me a crucial lesson. The endless debate about EF Core vs. Dapper is asking the wrong question. It’s not about which one is “better.” It’s about knowing which tool to grab for the job at hand. This isn’t about benchmarks; it’s about shipping features that are fast and easy to maintain.

Let’s break down how I decide in the real world.

EF Core: Your Go-To for Business Logic

I start every new project with EF Core. The productivity boost is just too massive to ignore. It shines when your main job is translating complex business rules into code.

Modeling Your Business, Not Just Tables

When your app has real business rules, you want your code to reflect that. EF Core’s mapping for C# objects (POCOs) is fantastic. Features like navigation properties, value objects, and owned types let you build a rich domain model that makes sense.

Think about an Order class. With EF Core, it’s clean and reflects the business.

public class Order
{ …