DbEye

DbEye is a lightweight middleware for ASP.NET Core that detects N+1 query problems and slow queries in Entity Framework Core applications — right in your development logs, per HTTP request.

⚠️ DbEye throws on startup if the current environment is not in the AllowedEnvironments list. By default, only Development is allowed.

Installation

dotnet add package DbEye

Setup

Add DbEye to your Program.cs:

builder.Services.AddDbEye();
builder.Services.AddDbContext<AppDbContext>((serviceProvider, options) =>
{
    options.AddInterceptors(serviceProvider.GetRequiredService<DbEyeInterceptor>());
});

app.UseDbEye();

Configuration

By default, queries taking longer than 500ms are flagged as slow, and 2 or more identical queries per request are flagged as N+1. You can customize all thresholds globally or per endpoint:

builder.Services.AddDbEye(options =>
{
    options.SlowQueryThresholdMs = 350;
    options.EndpointThresholds = new Dictionary<string, int>
    {
        { "/api/reports", 2000 },
        { "/api/comments", 200 }
    };
    options.NPlus1Threshold = 3;
    options.EndpointNPlus1Thresholds = new Dictionary<string, int>
    {
        { "/api/posts", 5 }
    };
    options.AllowedEnvironments = ["Development", "Staging"];
    options.ExcludeEndpoints("api/posts", "api/comments");
    options.ExcludeScalar();
    options.ExcludeSwagger();
});

Endpoints not listed in EndpointThresholds or EndpointNPlus1Thresholds fall back to the global threshold.

How it works

DbEye hooks into EF Core via an interceptor and analyzes query patterns on each request. When a problem is detected, a warning is emitted through ASP.NET Core's standard logging pipeline — it shows up directly in your terminal or VS Code output panel. When everything looks healthy, it logs a confirmation instead.

• N+1 detection — identifies when multiple identical queries are fired in a loop that could be resolved with a single join or Include()
• Slow query detection — flags queries that exceed the configured threshold
• Environment-aware — throws on startup if the current environment is not in AllowedEnvironments, zero overhead in production

No external dashboard, no extra dependencies to run — just clear warnings where you already look.

Example output

N+1 detected:

warn: DbEye[0]
      --------------------------------------------------
      ⚠️  N+1 detected at GET /api/posts
      Query repeated 5x - SELECT * FROM "Comments" WHERE "PostId" = ...
      --------------------------------------------------

Slow query detected:

warn: DbEye[0]
      --------------------------------------------------
      ⚠️  Slow query detected at GET /api/comments
      Duration: 732ms - SELECT * FROM "Comments"
      --------------------------------------------------

No issues:

info: DbEye[0]
      --------------------------------------------------
      ✅  GET /api/posts - no issues detected
      --------------------------------------------------

Try it out

The repository includes a demo project with a pre-configured Postgres database. Just clone and run:

git clone https://github.com/BrunoSync/DbEye
cd DbEye
docker compose up --build

The API will be available at http://localhost:5000. Watch the warnings in real time:

docker compose logs -f api

Triggering N+1

GET /api/posts without the include parameter fires one query per post to load comments:

curl http://localhost:5000/api/posts

To fix it, pass ?include=true — DbEye will stay silent:

curl http://localhost:5000/api/posts?include=true

Triggering a slow query

GET /api/comments with ?delay=true simulates a slow query:

curl http://localhost:5000/api/comments?delay=true

Other endpoints

Method	Endpoint	Description
GET	/api/posts	List posts (?include=true to avoid N+1)
GET	/api/posts/{id}	Get post by id
POST	/api/posts	Create post
PUT	/api/posts/{id}	Update post
DELETE	/api/posts/{id}	Delete post
GET	/api/comments	List comments (?delay=true to simulate slow query)
GET	/api/comments/{id}	Get comment by id
POST	/api/comments	Create comment
PUT	/api/comments/{id}	Update comment
DELETE	/api/comments/{id}	Delete comment

Supported databases

Database	Provider
PostgreSQL	Npgsql.EntityFrameworkCore.PostgreSQL
SQL Server	Microsoft.EntityFrameworkCore.SqlServer
SQLite	Microsoft.EntityFrameworkCore.Sqlite

Supported frameworks

Target	EF Core
.NET 8	8.x
.NET 9	9.x
.NET 10	10.x

Support

If DbEye saved you from a N+1 in production, consider buying me a coffee ☕

License

MIT