LiteDB is serverless database delivered in a single DLL (less than 350kb) fully written in .NET C# managed code. It is ideal for mobile apps or for small desktop/web apps, and its API is very similar to MongoDB C# Official Driver.
This code is linked to the post https://blog.georgekosmidis.net/2019/11/02/using-litedb-in-an-asp-net-core-api/ and has been updated to support .NET 8 and the latest LiteDB 5.0.19