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Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

chrisebert.net

41–50 of 60 posts

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#41
post #7

Can someone tell me why there isn't almost any laptop with Linux and ARM? Is it more efficient than x86 though

Chromebooks are essentially this, but not that great for local development.

So then one solution might be to buy a Chromebook, and put regular Linux on it? I don’t think the Chromebook are locked down.

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#42

Earlier quoted context omitted.

if imports are slow one should probably look into pre-compiling .pyc files into the Lambda bundle

This is a well known issue, and the fix is not to create any boto3 clients at runtime. Instead, ensure they're created globally (even if you throw them away) as the work then gets done once during the init period. The init period gets additional CPU allocation, so this is essentially "free" CPU. Source: I'm a former AWS employee.

Thanks for citing your sources, I think your source may be out if date, though! The “free init time hack” was killed in August (unless I’m missing something - never used it myself).

https://aws.amazon.com/blogs/compute/aws-lambda-standardizes...

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#43

Can someone tell me why there isn't almost any laptop with Linux and ARM? Is it more efficient than x86 though

It is a pain to make any new platform useful enough for large adoption. Apple made a lot of effort to get MacBook M1 useable, same for AWS with Graviton. Eventually it will be adopted for Linux laptops too, even without a specific vendor focusing on it, but it will take time.

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#44
post #2

It’s interesting that the author chose to use SHA256 hashing for the CPU intensive workload. Given they run on hardware acceleration using AES NI, I wonder how generally applicable it is. Still interesting either way though, especially since there were reports of earlier Graviton (pre v3) instances having mediocre AES NI performance.

Hardware-accelerated SHA support has a patchy history. I wrote an article some years ago about the prevalence of SHA instructions in x86 in x86_64 CPUs [0], like the current mess we see now with AVX-512, Intel invented something useful then declined to continue supporting it, while competitors that were late to the party became the real champions.

[0]: https://neosmart.net/blog/will-amds-ryzen-finally-bring-sha-...

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#45
I saw so many red flags:

- How is Rust only one order of magnitude faster than Python?

- How is Python that much faster than Node.js?

So I looked at the benchmark repo.

These benchmarks mean nothing folks!

Each of these benchmarks is just a SHA256 hash. This is NOT a valid way to compare CPUs, except if the only thing you will ever do with the CPU is to execute SHA256 hashes.

Hash functions are not representative of the performance of:

- Compression or decompression (of text, video, or anything really)

- Parsing

- Business logic (which is often dominated by pointer chasing)

So, you can safely ignore the claims of this post. They mean nothing.

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#46
This is very thorough, but I have a few things to add if you are using Node 22. I benchmarked Node 22 earlier this year using something similar to the light benchmark. https://speedrun.nobackspacecrew.com/blog/2025/07/21/the-fas...

I found that Node 22 had ~50ms slower coldstarts than Node 20. This is because the AWS Javascript V3 SDK loads the http request library which became much heavier in Node 22. This happens on the newly released Node 24 as well.

I recommend that if you are trying to benchmark coldstarts on Lambda, you measure latency from a client as well. The Init Duration in the logs doesn't include things like decrypting environment variables which adds ~20ms and other overhead like pulling the function code from S3. The impact of this manifests when comparing runtimes like llrt to Node, the Init Duration is faster than Node, but the E2E time from the client is actually closer because the llrt bundle size is 4-5MB larger than Node.

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#47
I'd be much more interested in bare metal ARM64 vs X64 workloads on modern hardware, remember the article that compared Hetzner VPN + Bare metal to Amazon workloads a while back?

Amazon was so ridiculously gimped and expensive that it was almost unfair, thus comparing ARM and X64 on Amazon thus runs into whatever arbitrary "savings" AWS does.

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#48
post #9

What I don't get is why is it that Node is dog slow . Seriously it seems borderline unusable. In terms of perf, Node has a pretty snappy JIT, and seems to perform OK in the browser, but this seems like something's not right here. ~200ms requests even in the light case are on the very brink of barely acceptable. On the other hand, Python performs very well, but it's alarming to see it gets slower in every release by a…

I have used nodejs quite a bit, and I would say it generally performs quite well. Its not as good at making the most out of monster hardware though.

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#49

Earlier quoted context omitted.

This is a well known issue, and the fix is not to create any boto3 clients at runtime. Instead, ensure they're created globally (even if you throw them away) as the work then gets done once during the init period. The init period gets additional CPU allocation, so this is essentially "free" CPU. Source: I'm a former AWS employee.

Thanks for citing your sources, I think your source may be out if date, though! The “free init time hack” was killed in August (unless I’m missing something - never used it myself). https://aws.amazon.com/blogs/compute/aws-lambda-standardizes...

Good callout that it's no longer free. However, you still get extra CPU, and assuming your execution environment isn't reloaded, that init time is amortized across all the invocations for the execution environment.

SnapStart is more widely available, which is the other option for shrinking the billed time spent in init (when I left, only Java SnapStart was available)

Re: Comparing AWS Lambda ARM64 vs. x86_64 Performance Across Runtimes in Late 2025

#50

I would not be surprised that Rust be faster than Python, but looking at the code of his Benchmarks, I'm not sure that it really means anything. For example, the "light" test will do calls to "dynamodb". Maybe you benchmark python, or you benchmark the aws sdk implementation with different versions of python, or just you benchmark average dynamodb latencies at different times of the day, ... And, at least for Python,…

I think the 'light' workload is the most realistic - most people use lambda as a stateless CRUD backend/REST endpoint, I don't think doing heavy number crunching is that idiomatic inside a lambda. And for that use case, Python seems almost as good as Rust, which is surprising to me, as is the fact that Node runs so slow - I have a ton of Node-based lambdas in prod, and while they're no speed demons, I'm quite surpris…

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