Why I'm Building a Database Engine in C# | Hacker News Reader

Why I'm Building a Database Engine in C#

nockawa.github.io

66 pointsvyrotek43 comments

> JIT warmup is real. The first call to any method pays the compilation cost. In a database engine, the first transaction after startup shouldn’t be 100x slower than the steady state.

Correct me if I'm wrong but isn't it what aot was supposed to solve?

AOT is a little fussy in real-world usage particularly for things like reflection. You can probably force it to work but it may make your code much uglier.

Span<T> is more important for performance TBH JIT warmup isn't a huge issue for a long-running process

    > ...but it may make your code much uglier

Flip side is that if you use more source generation, it may end up making the code more terse/"prettier" where it matters and avoid the reflection hit.

AI agents seem fairly good at generating source generators so there doesn't seem to be a reason to not use them.

With UnsafeAccessor you can often avoid reflection.

What's fussy about AOT and reflection?

Only a subset of reflection is actually AoT safe, and you can run into issues like "the method you wanted to call wasn't statically referenced anywhere, so there is no compiled implementation of it".

That's due to trimming which can be also be enabled for self-contained builds that use JIT compilation. Trimming is mandatory for AOT though. But you can use annotations to prevent trimming of specific thing.

AOT doesn't support generating new executable code at runtime (Reflection.Emit), like you can do in JIT mode.

As the sibling comment says, it's an effect of trimming which you get even without AOT.

In the section “Hardware-accelerated WAL checksums” he explains how the JIT compiles away the hardware support stuff depending on the exact capabilities of the system its on. With AOT you don’t get this - it’s way more coarse like x64 vs ARM

Eh, I don't see that as a huge deal because the first thing the DB has to do is warm up the disk cache, at least for the indexes. Of course the first call is slow.

Also worth mentioning are VeloxDB and RavenDB, both written in C#. TBF, I haven't used any of them... but aware they exist.

C# is pretty powerful and capable of lower level usage, such as in the examples given... not to mention a pretty nice interop with C-style libraries. It looks like the intent here might be a custom database engine for service integrations... not necessarily a full rdbms in and of itself.

Regarding tradeoffs:

I've been working with C# for most of my career, almost 25 years, since .Net 1.0. One of the huge things that I love about Rust is the lack of a runtime framework. I don't need to figure out how to bundle / ship / install a framework at runtime.

(I also like Cargo better than Nuget, but that's a very subjective opinion.)

Which leads to probably the biggest tradeoff:

> Typhon is an embedded...

It's probably hard, (or impossible) to use Typhon outside of the dotnet ecosystem. Granted, it's been years (since the 1.0 days) since I built a .dll that a native application could pull in, there are complications when you "impose" dotnet into an application that isn't dotnet. These don't happen when your library is 100% native, which you get with C/C++/Rust.

I think the developer is specifically targeting running in game engines in Unity, because that's already a C# capable environment.

Personally I'm not worried about the micro optimization, I'm more a "why are you attempting to compete with sqlite" person.

> One of the huge things that I love about Rust is the lack of a runtime framework. I don't need to figure out how to bundle / ship / install a framework at runtime.

Rust has a runtime, it's just tiny and auto-bundled (for now). Modern .NET's support for self-contained bundling has gotten pretty good. AOT is getting better too, and AOT-ready code (switch Reflection for Source Generators as much as possible, for instance) can do some very heavy treeshaking of the runtime.

Also, yeah native embedding has gotten somewhat easier in recent years depending on the style of API you want to present to native code. Furthermore both Godot and Unity (differently) embed .NET/C# as options in game development. I certainly expect Typhon is primarily targeting Godot and/or (eventually) Unity (when it finishes switching to coreclr to support more of these features) embedding (but maybe also Stride, a fully C# game engine).

>But what about GC pauses

GC is like auto transmission, it's an inevitable natural evolution of programming languages.

I think the future of programming languages will have hybrid modes of GC and manual, similar to today's hybrid auto transmission automatic and manual in state-of-the-art hypercar [1]. I considered D language as pioneer in this innovative approach.

My hypothesis is that GC can be made deterministic like manual memory management, just like how ICE auto industry minimize the manual transmission. Heck, no manual for EV.

Hopefully the new io_uring facility with BPF controlled can enable this deterministic GC [2],[3].

[1] Here’s how Koenigsegg’s new manual/automatic CC850 gearbox work (2025):

https://www.topgear.com/car-news/supercars/heres-how-koenigs...

[2] BPF meets io_uring (2026):

https://lwn.net/Articles/847951/

[3] How io_uring and eBPF Will Revolutionize Programming in Linux (2020):

https://www.scylladb.com/2020/05/05/how-io_uring-and-ebpf-wi...

We have a pretty fast InMemory Database for .Net as well, named InMemory.Net!

I wonder why he didn't use AOT compiling if he's worried about JIT warmup.

It wasn't discussed, so we're left to speculate. If I had to guess, I imagine that the .NET JIT has actual benefits: the variety of architectures has gotten enormous and JIT is likely a performance win after warmup.

.NET JIT supports dynamic PGO.

My guess is because .NET AoT is not yet optimized and mature enough as JIT. This is known and is on the agenda of Microsoft but it will take time to get there.

I would be less worried about the GC pause, than the need to reserve some memory for garbage collection. Any reduction in available memory is going to tend to mean a hit to performance.

C# is a great language with almost unlimited power and great ergonomics (as the article shows), but the .NET CLR (runtime) is a bit overcomplicated with a distinct "Java smell", and packaging and distribution is still meh.

If they could make the developer experience similar to Go, it would rule the world...

I drank the Go kool-aid, then tried to do some high performance things the Go way: didn't work (channels are slow) and I got over it. Still think Go is great for web backends and the like with production grade stdlib.

Great post with details, not a I'm vibe coding...

> tried to do some high performance things the Go way: didn't work (channels are slow) and I got over it.

What did you choose instead?

> If they could make the developer experience similar to Go, it would rule the world...

You can already AOT compile .NET software to an executable to run on whichever platform you need, just like Go.

Libraries need to be published into a package manager (NuGet) which is more friction than just importing from Git repos but it's not that bad.

AOT is not a panacea and comes with some restrictions/trade-offs that need understood before depending on it in production.

Losing dynamic PGO by using AOT compilation could be a detriment to performance in long-running applications, right?

You also have the option to do single file deployment where it self-extracts the runtime when you run it. It's not as nice but it works and maintains full compatibility.

While that is nice it’s not AOT, is it?

Yes, but it's still a single-file deployment option that can easily cross-compile. Just with slower startups.

wouldn't you have the same restrictions/tradeoffs using go (or other compiled languages)?

I've never used go, am curious

Pretty much, yes. For example reflection is severely limited in .NET AOT vs. JIT, runtime generated code is more common than you'd think and cannot be done AOT. Go was designed for AOT so they already built everything around the limitations because it never supported more.

It'll just take time for .NET to catch up where the dependencies you need automatically work with AOT builds.

shaddap

I actually really like the CLR developer experience next to java ngl. I reach for C# in lieu of java (less J2EE SingletonBeanFactoryManagerInstance slop) but particularly F# is pretty nice to use. Haskell has bad tooling, OCaml is getting better thanks to JaneStreet (and if OxCaml gets wide adoption unboxed types are a big perf win) but if nothing else lack of a Rider-esque debugger is just a big time sink.

That seems great, I have seen a few similar dbs written in java that say the same thing, that when written correctly you can get the perf very close to C, but at that point you are just writing C with a different syntax. You don't win on any in the security guarantees, so at that point can we just not build everything in wasm and then we can interface it from both dotnet and the jvm?

I'd say modern C++ is high level and ergonomic enough to stop considering any language with a GC.

Does C++ have build in memory management now?

It's a part of the Standard Library - Smart Pointers.

Am amused that someone feels compelled to justify writing a db in C#. Such conscientiousness!

I'm not sure authors of Cassandra, ElasticSearch, MongoDB (and more...?) ever had the slightest twinge of uncertainty about whether a managed memory env would cause far more problems than it fixed, even with less native tooling than in C#. Java bros DGAF

Mongo’s c++ isn’t it?

Yes

oh. sorry, had a decent excuse for its horribility, now i have less of one.

You do you.

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