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
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...
Reposted by Alfonso Subiotto
We're excited to share that the Parca Agent now works offline! Store CPU profiles locally when disconnected, upload when ready. Because not all computing happens in data centers.
Read how we built it: www.polarsignals.com/blog/posts/2...
Read how we built it: www.polarsignals.com/blog/posts/2...
Offline Mode for the Parca Agent
Collect and upload profiles -- even without a network connection
www.polarsignals.com
August 7, 2025 at 2:49 PM
We're excited to share that the Parca Agent now works offline! Store CPU profiles locally when disconnected, upload when ready. Because not all computing happens in data centers.
Read how we built it: www.polarsignals.com/blog/posts/2...
Read how we built it: www.polarsignals.com/blog/posts/2...
New storage format RFC in the works 👀 Early preview:
July 31, 2025 at 12:31 PM
New storage format RFC in the works 👀 Early preview:
Reposted by Alfonso Subiotto
🚀 Today, we're excited to launch Off-CPU profiling! Check out our blog on what we needed to do to make it most useful and how you can get started with it! 🧊
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Introducing Off-CPU Profiling
How Off-CPU profiling works and how to get the most out of it
www.polarsignals.com
July 30, 2025 at 3:26 PM
🚀 Today, we're excited to launch Off-CPU profiling! Check out our blog on what we needed to do to make it most useful and how you can get started with it! 🧊
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
@metalmatze.de built an MCP server so you can hook up your agent to your profiling data. Check it out!
🔥 Have you ever stared at a flame graph wondering why your app is slow?
Using the new @PolarSignalsIO MCP, you can now ask "Why is my service slow?" and e.g. @anthropic.com's Claude Code or @cursor.com.web.brid.gy will analyze your production profiles and suggest code fixes.
Using the new @PolarSignalsIO MCP, you can now ask "Why is my service slow?" and e.g. @anthropic.com's Claude Code or @cursor.com.web.brid.gy will analyze your production profiles and suggest code fixes.
July 18, 2025 at 7:34 AM
@metalmatze.de built an MCP server so you can hook up your agent to your profiling data. Check it out!
Reposted by Alfonso Subiotto
📔Writing our Rust database from scratch gave us a golden opportunity to implement deterministic simulation testing as a core feature. Learn about the architecture that gives us full control over DST ingredients. 🧊
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Deterministic Simulation Testing in Rust: A Theater Of State Machines
How we designed our database for complete control over concurrency, time, randomness, and failure injection.
www.polarsignals.com
July 8, 2025 at 2:15 PM
📔Writing our Rust database from scratch gave us a golden opportunity to implement deterministic simulation testing as a core feature. Learn about the architecture that gives us full control over DST ingredients. 🧊
www.polarsignals.com/blog/posts/2...
www.polarsignals.com/blog/posts/2...
Writing our Rust database from scratch gave us a golden opportunity to implement deterministic simulation testing as a core feature. I wrote a blog post about the architecture that gives us full control over concurrency, time, randomness, and failure injection. (link in comment)
July 8, 2025 at 2:25 PM
Writing our Rust database from scratch gave us a golden opportunity to implement deterministic simulation testing as a core feature. I wrote a blog post about the architecture that gives us full control over concurrency, time, randomness, and failure injection. (link in comment)
If you're serious about performance, you need continuous profiling in your life
July 7, 2025 at 2:02 PM
If you're serious about performance, you need continuous profiling in your life
Nice read about how maybe it's time to delete some tests (not your DST test though): andre.arko.net/2025/06/30/y...
You should delete tests
We’ve had decades of thought leadership around testing, especially coming from wholistic development philosophies like Agile, TDD, and BDD. After all that time and several supposedly superseding…
andre.arko.net
July 7, 2025 at 7:35 AM
Nice read about how maybe it's time to delete some tests (not your DST test though): andre.arko.net/2025/06/30/y...
Reposted by Alfonso Subiotto
This was a fun read. Speed runs building a cloud DB. Hill climbing the design can lead to a local maximum. Lots of lessons. Now I need to read their next post on the new one!
July 4, 2025 at 5:53 PM
This was a fun read. Speed runs building a cloud DB. Hill climbing the design can lead to a local maximum. Lots of lessons. Now I need to read their next post on the new one!
Looking forward to speaking at @eurorust.eu about the deterministic simulation testing we're doing at @polarsignals.com!
Haunted by that one production bug you just can’t reproduce? This talk is for you.
At #EuroRust25, @asubiotto.bsky.social will show how deterministic simulation testing lets you find and replay bugs before they hit prod.
🧵1/3
At #EuroRust25, @asubiotto.bsky.social will show how deterministic simulation testing lets you find and replay bugs before they hit prod.
🧵1/3
July 4, 2025 at 9:44 AM
Looking forward to speaking at @eurorust.eu about the deterministic simulation testing we're doing at @polarsignals.com!
Reposted by Alfonso Subiotto
Our very own @asubiotto.bsky.social for the first time publicly talking about the DST approach we’re taking in our new database.
(Blog post coming soon as well!)
(Blog post coming soon as well!)
June 20, 2025 at 11:31 AM
Our very own @asubiotto.bsky.social for the first time publicly talking about the DST approach we’re taking in our new database.
(Blog post coming soon as well!)
(Blog post coming soon as well!)
You know that urge to rewrite your database in Rust? We gave in.
(Link in comment)
(Link in comment)
June 18, 2025 at 3:15 PM
You know that urge to rewrite your database in Rust? We gave in.
(Link in comment)
(Link in comment)
Off to Systems Distributed. See you in Amsterdam!
June 18, 2025 at 10:53 AM
Off to Systems Distributed. See you in Amsterdam!
Quis verificabit ipsos verificatores?
June 12, 2025 at 9:07 AM
Quis verificabit ipsos verificatores?
Claude code seems to love debugging by pointing at random code paths it doesn't understand and saying "the root cause is now clear"
June 10, 2025 at 7:01 AM
Claude code seems to love debugging by pointing at random code paths it doesn't understand and saying "the root cause is now clear"
Reposted by Alfonso Subiotto
We've been working hard to enhance our continuous profiling for GPUs. Learn about more metrics (like PCIe throughput) and the upcoming On-GPU profiles.
If you are attending ai.engineer, come and stop by our booth S18 to discuss all of these features!
www.polarsignals.com/blog/posts/2...
If you are attending ai.engineer, come and stop by our booth S18 to discuss all of these features!
www.polarsignals.com/blog/posts/2...
Latest in Continuous Profiling for GPUs
Attending ai.engineer 2025 in San Francisco
www.polarsignals.com
June 4, 2025 at 7:59 PM
We've been working hard to enhance our continuous profiling for GPUs. Learn about more metrics (like PCIe throughput) and the upcoming On-GPU profiles.
If you are attending ai.engineer, come and stop by our booth S18 to discuss all of these features!
www.polarsignals.com/blog/posts/2...
If you are attending ai.engineer, come and stop by our booth S18 to discuss all of these features!
www.polarsignals.com/blog/posts/2...