Alfonso Subiotto
@asubiotto.com
Engineering at polarsignals.com & investing in devtools/data/infra
at lorimerventures.com | Previously tech lead at cockroachlabs.com
at lorimerventures.com | Previously tech lead at cockroachlabs.com
@polarsignals.com is joining @dash0.com! We'll be integrating continuous profiling into Dash0 and replacing ClickHouse with Great Lakes, the storage engine we built to power Polar Signals.
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Polar Signals is Joining Dash0 | Polar Signals
The next chapter for continuous profiling, our database, and the team
www.polarsignals.com
August 18, 2026 at 2:00 PM
@polarsignals.com is joining @dash0.com! We'll be integrating continuous profiling into Dash0 and replacing ClickHouse with Great Lakes, the storage engine we built to power Polar Signals.
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
This was a fun one! For @polarsignals.com's latest hackathon, I wrote an FSST decompression CUDA kernel and then optimized it by profiling with our new GPU PC sampling feature.
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
My Journey Optimizing a CUDA Kernel with Polar Signals | Polar Signals
A storage engineer's descent into warp stalls, memory throttles, and aligned stores
www.polarsignals.com
June 24, 2026 at 2:27 PM
This was a fun one! For @polarsignals.com's latest hackathon, I wrote an FSST decompression CUDA kernel and then optimized it by profiling with our new GPU PC sampling feature.
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
If you're doing any performance work on GPUs, this is huge. PC sampling is a powerful tool for GPU optimization, but causes serial kernel executions.
We've released production-ready continuous PC sampling so you can get GPU performance insights on your production workloads.
We've released production-ready continuous PC sampling so you can get GPU performance insights on your production workloads.
🚀 Launching today: GPU PC sampling in production. Instruction-level profiling telling you why and where warps stall. Whether it is memory latency, scoreboard waits, or barriers. 🧊
Previously NSight-only territory. Now running in prod with low overhead.
www.polarsignals.com/blog/posts/2...
Previously NSight-only territory. Now running in prod with low overhead.
www.polarsignals.com/blog/posts/2...
Open-Source Low-Overhead NVIDIA CUDA PC Sampling | Polar Signals
And how we made it happen
www.polarsignals.com
June 10, 2026 at 3:16 PM
If you're doing any performance work on GPUs, this is huge. PC sampling is a powerful tool for GPU optimization, but causes serial kernel executions.
We've released production-ready continuous PC sampling so you can get GPU performance insights on your production workloads.
We've released production-ready continuous PC sampling so you can get GPU performance insights on your production workloads.
Reposted by Alfonso Subiotto
New Blog Alert! Learn how we overcame eBPF limits to unwind deeply nested PyTorch training stacks and learned some cools things along the way:
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Python Zebra Stacks | Polar Signals
Unwinding Deep PyTorch Training Stacks with eBPF
www.polarsignals.com
May 20, 2026 at 1:56 PM
New Blog Alert! Learn how we overcame eBPF limits to unwind deeply nested PyTorch training stacks and learned some cools things along the way:
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Reposted by Alfonso Subiotto
🤖Using Polar Signals Cloud and Claude Code to autonomously optimize your code every day! 📈
Also: Check out our new website! What do you think?
www.polarsignals.com/blog/posts/2...
Also: Check out our new website! What do you think?
www.polarsignals.com/blog/posts/2...
Autonomous Optimization with Claude Code | Polar Signals
Optimize your infrastructure autonomously every day with Claude Code and Polar Signals
www.polarsignals.com
May 6, 2026 at 1:42 PM
🤖Using Polar Signals Cloud and Claude Code to autonomously optimize your code every day! 📈
Also: Check out our new website! What do you think?
www.polarsignals.com/blog/posts/2...
Also: Check out our new website! What do you think?
www.polarsignals.com/blog/posts/2...
We've been working on a major schema migration at @polarsignals.com that has unlocked some pretty wild improvements. Apart from a 50% (!!) reduction in storage size thanks to logical compression in vortex.dev, there has been a dramatic improvement in query performance.
April 28, 2026 at 9:52 AM
We've been working on a major schema migration at @polarsignals.com that has unlocked some pretty wild improvements. Apart from a 50% (!!) reduction in storage size thanks to logical compression in vortex.dev, there has been a dramatic improvement in query performance.
Reposted by Alfonso Subiotto
Tired of Node.js flamecharts full of `a`, `m`, and `_0x3f2`? We just shipped source maps support for Node.js profiles in Polar Signals Cloud.
Just add a plugin to your build pipeline, and your profiles show the real code.
Know more: www.polarsignals.com/blog/posts/2...
Just add a plugin to your build pipeline, and your profiles show the real code.
Know more: www.polarsignals.com/blog/posts/2...
Do more with less. | Polar Signals
Polar Signals Cloud is an always-on, zero-instrumentation continuous profiling for CPU, GPU, and Memory that helps improve performance, understand incidents, and lower infrastructure costs.
www.polarsignals.com
April 15, 2026 at 1:13 PM
Tired of Node.js flamecharts full of `a`, `m`, and `_0x3f2`? We just shipped source maps support for Node.js profiles in Polar Signals Cloud.
Just add a plugin to your build pipeline, and your profiles show the real code.
Know more: www.polarsignals.com/blog/posts/2...
Just add a plugin to your build pipeline, and your profiles show the real code.
Know more: www.polarsignals.com/blog/posts/2...
I'm happy to share that I will be speaking at #QConLondon on March 16 on deterministic simulation testing at Polar Signals. For anyone interested in attending: SPEAKER60QUK26 for £60 off
February 17, 2026 at 3:02 PM
I'm happy to share that I will be speaking at #QConLondon on March 16 on deterministic simulation testing at Polar Signals. For anyone interested in attending: SPEAKER60QUK26 for £60 off
Claude is down. I guess I have to learn how to code again.
January 14, 2026 at 9:45 AM
Claude is down. I guess I have to learn how to code again.
Reposted by Alfonso Subiotto
📢 It’s a new year so we’re announcing something new which is the Sandwich view: A way to visualize a function’s callers and callees side by side for better debugging and performance work. Read more about it here: www.polarsignals.com/blog/posts/2...
Introducing the Sandwich View
A new way to visualize a function’s callers and callees side by side.
www.polarsignals.com
January 8, 2026 at 3:45 PM
📢 It’s a new year so we’re announcing something new which is the Sandwich view: A way to visualize a function’s callers and callees side by side for better debugging and performance work. Read more about it here: www.polarsignals.com/blog/posts/2...
My EuroRust talk has been uploaded to YT! I cover how we architected our Rust database at @polarsignals.com as a set of state machines to enable deterministic simulation testing and catch hard-to-reproduce bugs before they hit prod.
A new talk is out! 🙌 @asubiotto.com shows how deterministic simulation testing (DST) uses random seeds and state machines to explore countless execution paths—and reliably replay failures when things go wrong 🦀🎲
👉 youtu.be/V12hHoagv-E
👉 youtu.be/V12hHoagv-E
Random Seeds and State Machines - Alfonso Subiotto | EuroRust 2025
Random Seeds and State Machines: An Approach to Deterministic Simulation Testing - Alfonso Subiotto at EuroRust 2025
Have you spent sleepless nights thinking about that heisenbug in production that…
youtu.be
January 7, 2026 at 11:46 AM
My EuroRust talk has been uploaded to YT! I cover how we architected our Rust database at @polarsignals.com as a set of state machines to enable deterministic simulation testing and catch hard-to-reproduce bugs before they hit prod.
A simple 50-line code change saves us 30% of CPU across our whole infrastructure. This is the magic of system-wide profiling with @polarsignals.com. Easy to spot, easy to fix.
performance[vortex-array]: don't call is_valid to count bytes in varbinview by asubiotto · Pull Request #5814 · vortex-data/vortex
I noticed that the better blocks compressor uses count_referenced_bytes which calls is_valid on each view and results in an expensive scalar_at call. This was 30% of our system-wide CPU usage over ...
github.com
December 23, 2025 at 10:48 AM
A simple 50-line code change saves us 30% of CPU across our whole infrastructure. This is the magic of system-wide profiling with @polarsignals.com. Easy to spot, easy to fix.
Reposted by Alfonso Subiotto
🚀 We recently announced our NVIDIA CUDA always-on profiler. Check out this blog on how to try it out super quickly with your CUDA workload today!🧊
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Profiling NVIDIA CUDA in Kubernetes
The easiest way to get started Profiling CUDA in Kubernetes
www.polarsignals.com
December 18, 2025 at 3:59 PM
🚀 We recently announced our NVIDIA CUDA always-on profiler. Check out this blog on how to try it out super quickly with your CUDA workload today!🧊
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Happy to share that I've been nominated to the Vortex Technical Steering Committee! It's been fun and productive switching to Vortex from Parquet as our storage format @polarsignals.com and I'm excited to continue contributing to the Vortex project.
vortex.dev/blog/novembe...
vortex.dev/blog/novembe...
November Bulletin | Vortex Blog
Overview of all work happening in Vortex
vortex.dev
December 15, 2025 at 3:03 PM
Happy to share that I've been nominated to the Vortex Technical Steering Committee! It's been fun and productive switching to Vortex from Parquet as our storage format @polarsignals.com and I'm excited to continue contributing to the Vortex project.
vortex.dev/blog/novembe...
vortex.dev/blog/novembe...
Reposted by Alfonso Subiotto
🧊 New on the Polar Signals Blog — Our Delta Lake Fork
Purpose-built for our continuous profiling product. In our latest post, we walk through how Delta Lake works, and the changes we've made to improve performance for our product.
👉 Read the full post: buff.ly/KwHINtO
Purpose-built for our continuous profiling product. In our latest post, we walk through how Delta Lake works, and the changes we've made to improve performance for our product.
👉 Read the full post: buff.ly/KwHINtO
Great Lakes: A Delta Lake Fork
Our updates to Delta Lake Table Format
www.polarsignals.com
December 4, 2025 at 2:45 PM
🧊 New on the Polar Signals Blog — Our Delta Lake Fork
Purpose-built for our continuous profiling product. In our latest post, we walk through how Delta Lake works, and the changes we've made to improve performance for our product.
👉 Read the full post: buff.ly/KwHINtO
Purpose-built for our continuous profiling product. In our latest post, we walk through how Delta Lake works, and the changes we've made to improve performance for our product.
👉 Read the full post: buff.ly/KwHINtO
Sometimes an interface is so ubiquitous that performance limitations inherent to its design are just accepted. This has been our experience with Parquet. We switched to Vortex which aligned much better with our needs and saw a 70% performance improvement across the board. Read more below 👇
Do more with less. | Polar Signals
Polar Signals Cloud is an always-on, zero-instrumentation continuous profiling for CPU, GPU, and Memory that helps improve performance, understand incidents, and lower infrastructure costs.
www.polarsignals.com
November 25, 2025 at 3:31 PM
Sometimes an interface is so ubiquitous that performance limitations inherent to its design are just accepted. This has been our experience with Parquet. We switched to Vortex which aligned much better with our needs and saw a 70% performance improvement across the board. Read more below 👇
Reposted by Alfonso Subiotto
Ever wondered how your browser devtools jumps from bundle.min.js:1:27698 → src/index.ts:73:16? 🧊
We unpack the internals of JS Source Maps: Base64 VLQ encoding, mapping deltas, and how your original TS code gets reconstructed from minified bundles.
🔗 www.polarsignals.com/blog/posts/2...
We unpack the internals of JS Source Maps: Base64 VLQ encoding, mapping deltas, and how your original TS code gets reconstructed from minified bundles.
🔗 www.polarsignals.com/blog/posts/2...
The Inner Workings of JavaScript Source Maps
A deep dive into how JavaScript source maps work under the hood, with examples showing how all the pieces fit together.
www.polarsignals.com
November 4, 2025 at 3:07 PM
Ever wondered how your browser devtools jumps from bundle.min.js:1:27698 → src/index.ts:73:16? 🧊
We unpack the internals of JS Source Maps: Base64 VLQ encoding, mapping deltas, and how your original TS code gets reconstructed from minified bundles.
🔗 www.polarsignals.com/blog/posts/2...
We unpack the internals of JS Source Maps: Base64 VLQ encoding, mapping deltas, and how your original TS code gets reconstructed from minified bundles.
🔗 www.polarsignals.com/blog/posts/2...
Introducing the world's first open source continuous NVIDIA CUDA profiler. Zero code changes required, low overhead, and always on.
🚀 We're super excited to launch NVIDIA CUDA Profiling today! Check out the blog on how we made it happen! 🧊
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Continuous NVIDIA CUDA Profiling In Production
Low-Overhead Profiling of GPUs with USDT Probes and eBPF
www.polarsignals.com
October 22, 2025 at 2:28 PM
Introducing the world's first open source continuous NVIDIA CUDA profiler. Zero code changes required, low overhead, and always on.
Reposted by Alfonso Subiotto
Took advantage of the lunch break to replay this great talk by Alfonso Subiotto (@asubiotto.com) making the case for a State Machines based approach to Deterministic Simulation Testing, being used at @polarsignals.com, very interesting!
Their inspiration for this: sled.rs/simulation
Their inspiration for this: sled.rs/simulation
October 10, 2025 at 11:23 AM
Took advantage of the lunch break to replay this great talk by Alfonso Subiotto (@asubiotto.com) making the case for a State Machines based approach to Deterministic Simulation Testing, being used at @polarsignals.com, very interesting!
Their inspiration for this: sled.rs/simulation
Their inspiration for this: sled.rs/simulation
Reposted by Alfonso Subiotto
We're excited to be at @rustconf.com 2025!
Let's talk about profiling Rust with zero compromise!
#rustconf25
Let's talk about profiling Rust with zero compromise!
#rustconf25
September 3, 2025 at 7:13 PM
We're excited to be at @rustconf.com 2025!
Let's talk about profiling Rust with zero compromise!
#rustconf25
Let's talk about profiling Rust with zero compromise!
#rustconf25
Reposted by Alfonso Subiotto
We recently made some performance improvements to our Flame Graph by implementing backend pre-computation and viewport culling. Read more in our latest blog post: www.polarsignals.com/blog/posts/2...
Parallel Flame Graph Rendering
How we improved our flame graph rendering by moving computation to the backend.
www.polarsignals.com
September 3, 2025 at 2:39 PM
We recently made some performance improvements to our Flame Graph by implementing backend pre-computation and viewport culling. Read more in our latest blog post: www.polarsignals.com/blog/posts/2...
I wrote about why we should treat German string encoding/StringViews as Just Another Encoding™
German strings 🇩🇪 have become very popular in the database world. However, they're not a silver bullet. Read more in our latest blog post:
Das Problem mit German Strings
And why I don't want my database to choose the best encoding for me (yet)
www.polarsignals.com
August 26, 2025 at 4:00 PM
I wrote about why we should treat German string encoding/StringViews as Just Another Encoding™
Do any database systems "columnarize" the German string encoding so rather than storing a 16-byte view for each element which includes length+prefix+pointer you'd store all lengths together, prefixes together etc...? Seems like prefix operations would be more SIMD friendly.
August 20, 2025 at 11:45 AM
Do any database systems "columnarize" the German string encoding so rather than storing a 16-byte view for each element which includes length+prefix+pointer you'd store all lengths together, prefixes together etc...? Seems like prefix operations would be more SIMD friendly.
The hardest part about writing a blog post is the introduction. Here I am, 4 hours later.
August 19, 2025 at 12:18 PM
The hardest part about writing a blog post is the introduction. Here I am, 4 hours later.
Reposted by Alfonso Subiotto
Tame the OOM killer with OOMProf, the new eBPF memory profiler for Go programs being taken out by the kernels OOM killer!
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
OOMProf - Profiling on the Brink
Using eBPF to record your programs dying breathes
www.polarsignals.com
August 13, 2025 at 2:49 PM
Tame the OOM killer with OOMProf, the new eBPF memory profiler for Go programs being taken out by the kernels OOM killer!
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...