iiinova — where your digital self keeps evolving

Joe Hellerstein @joehellerstein.bsky.social · 07/04/2026

It turns out that the 'weakest' tic-tac-toe opening is actually the best one — if your opponent occasionally makes mistakes. New post on what games can teach us about coordination cost in distributed systems: jhellerstein.github.io/blog/two-com...

jhellerstein.github.io

Playing for Complications—and Why Systems Shouldn't

In the last post I argued that coordination is commitment—a vow to avoid futures with undesirable outcomes. I also raised a question: when coordination is…

060

Joe Hellerstein @joehellerstein.bsky.social · 11/02/2026

📄 New blog post! AI will soon write most distributed code. Distributed code is where our worst bugs —Heisenbugs— live. The real lever isn’t “test more,” it’s **aim better**: AI should target frameworks where correctness contracts are explicit and checkable. jhellerstein.github.io/blog/codegen...

jhellerstein.github.io

Coding Agents Meet Distributed Reality

AI is about to write most of the code in the world. Most of the code in the world participates in a distributed system. And distributed code is where our worst…

0112

Reposted by Joe Hellerstein

Madelon Hulsebos @madelonhulsebos.bsky.social · 05/06/2025

Let’s collaborate on democratizing insights from tabular data in Amsterdam! ✨ PhD directions: 1) fundamental techniques for tabular foundation models, 2) reliable mechanisms for AI-powered tabular data analysis. Sharing w/ friends appreciated! ⬇️

233

Joe Hellerstein @joehellerstein.bsky.social · 05/06/2025

The last blog post in my miniseries on CRDTs is up! jhellerstein.github.io/blog/crdt-in... Mix of pragmatism and formalism. There's actually a small result in there that may be novel: Strong Eventual Consistency !=> Determinism. Curious to hear whether they've seen this result elsewhere.

jhellerstein.github.io

CRDTs #4: Convergence, Determinism, Lower Bounds and Inflation

The CRDT literature sometimes leaves room for mathematical ambiguity. Maybe because the bulk of the work tends to be targeted at systems researchers and…

0122

Joe Hellerstein @joehellerstein.bsky.social · 28/05/2025

posted today! BTW I peeked at the automerge Rust? Collaborative editing is an example where one probably *has* to resort to unsafe behavior (you're the expert there!) so I'm mostly advocating for more encapsulation/comments in that case. jhellerstein.github.io/blog/crdt-do...

jhellerstein.github.io

CRDTs #3: Do Not Read!

Ever used a CRDT, thought you were safe, and—boom—you bought a Ferrari you didn't mean to? It could happen to you! The truth is that CRDTs are dangerous to…

054

Joe Hellerstein @joehellerstein.bsky.social · 25/05/2025

Really early and well seen, definitely influenced me and my team! Hats off.

010

Joe Hellerstein @joehellerstein.bsky.social · 25/05/2025

Depends what you want the “set of lists” semantics to mean. I’d think you likely want a 2P-map lattice of RGAs (2P-map would be like a 2P-set but with a lattice value associated with each unique item in adds). If you want more detail please comment in the blog so it’s easier for others to find it.

000

Joe Hellerstein @joehellerstein.bsky.social · 25/05/2025

There are simple and helpful composites that can be written generically and reused safely. E.g. lattice pairs (free or lexical) and Map lattices. Helps to have a language with good support for generics (parameterized types).

100

Joe Hellerstein @joehellerstein.bsky.social · 23/05/2025

(Catching up to my LI feed). Next blog post is out! This is the first real post in a short series on CRDTs, an idea that has some currency in the distributed programming community, but one that comes with a number of sharp edges. Be careful out there! jhellerstein.github.io/blog/crdt-tu...

jhellerstein.github.io

CRDTs #1: Turtles All the Way Down

This is the 1st post in a series of 4 detailed posts I'm doing on CRDTs. Please see the intro post for context. Modern distributed systems often seem to rest on…

1123

Joe Hellerstein @joehellerstein.bsky.social · 23/05/2025

Blog relaunch! Bbye wordpress, hello github. If you're into SW dev, cloud, databases, distributed systems, automatic codegen ... or data and CS in general... check it out. As a warmup, I'm starting with a series of posts on CRDTs. Intro post up now: jhellerstein.github.io/blog/crdt-in...

jhellerstein.github.io

A Run of CRDT Posts

Over the next few days, I'm going to post a number of observations about CRDTs: Convergent Replicated Data Types. These are data structures that aspire to help…

2185

Joe Hellerstein @joehellerstein.bsky.social · 16/04/2025

Wow! @arvind.bsky.social giving an awesome keynote including discussion of VegaExpress and GoFish interactive vis libraries from his group. #EPICRetreat #UCBerkeley.

020

Joe Hellerstein @joehellerstein.bsky.social · 16/04/2025

Here’s a provocative example from JD Zamfirescu-Pereira on ways that humans and LLMs can get misaligned on expectations. Is the LLM lying? Is it just emitting tokens? How do people interpret this? #EPICRetreat #UCBerkeley.

120

Reposted by Joe Hellerstein

Shadaj Laddad @shadaj.me · 13/02/2025

The SF Systems Meetup is back! On 2/27, we're excited to have headline talks from the creator of FizzBee and a research collaborator with Signal. This is going to be a super fun night diving deep into making distributed protocols work, hope you'll join us! lu.ma/vqjf30k3

lu.ma

SF Systems Meetup: Correctness and Security for Distributed Systems · Luma

The SF Systems Meetup is back for the new year! This meetup, our theme is correctness and security. It's easy to write a distributed protocol, but very hard to…

053

Joe Hellerstein @joehellerstein.bsky.social · 13/02/2025

The question: "what are examples of commutative functions that are not associative?" GPT4 was funny, thinking aloud and then proving itself wrong:

GPT4 asserts that Min and Max functions are commutative but not associative, but then checks itself and backtracks.

100

Joe Hellerstein @joehellerstein.bsky.social · 13/02/2025

In some kind of sad watershed, today was the day as a professor when I live-ChatGPT'ed the answer to a question in a Zoom with my PhD student and his undergrad mentees. But hey, let's paint it in a positive light: this was a demonstration of using the right tool at the right time.

150

Reposted by Joe Hellerstein

Eric Colson @ecolson.bsky.social · 06/02/2025

Operationalizing Machine Learning: An Interview Study by @joehellerstein.bsky.social, @adityagp.bsky.social, et al. Particularly love the part on "Retrofitting Explanations". #MachineLearning #MLOps #Datascience. arxiv.org/pdf/2209.09125

1114

Joe Hellerstein @joehellerstein.bsky.social · 28/01/2025

I think “getting all of your coordination under one roof” (or behind a unified api or something) is the message I’m hearing from you. Don’t know if that helps?

000

Joe Hellerstein @joehellerstein.bsky.social · 24/01/2025

A muddled post at best. A sequential log *is* a point of coordination. It doesn't avoid coordination as claimed, it just centralizes it in 1 service (and arguably encourages overuse). Coordination avoidance is orthogonal: discover when global ordering is not needed. Ie avoidance avoids the log!

280

Joe Hellerstein @joehellerstein.bsky.social · 23/01/2025

Sunset in #Berkeley these days is a perfect field goal over the golden gate bridge. Shifts quite a ways north during the summer.

090

Reposted by Joe Hellerstein

Jamie McCarty @jamiemccarty.bsky.social · 30/12/2024

It’s incredibly beautiful that President Carter is our emissary on a Voyager probe. His words live on across our galaxy!

818242

Joe Hellerstein @joehellerstein.bsky.social · 30/12/2024

The culture in my community in CS has long been to share course materials openly. My lecture videos+notes are all posted public online, as are those of many of my peers. If anything there's some competition for attention. No judgement implied, just interesting difference in community norms.

010

Reposted by Joe Hellerstein

Shadaj Laddad @shadaj.me · 03/12/2024

Thrilled to share that our paper “Flo: A Semantic Foundation for Progressive Stream Processing” (with @mpmilano.bsky.social, Alvin Cheung, and @joehellerstein.bsky.social) will appear at POPL 2025! Check out the preprint at arxiv.org/abs/2411.08274, and read on for more!

arxiv.org

Flo: a Semantic Foundation for Progressive Stream Processing

Streaming systems are present throughout modern applications, processing continuous data in real-time. Existing streaming languages have a variety of semantic models and guarantees that are often inco...

14412

Joe Hellerstein @joehellerstein.bsky.social · 03/12/2024

Sunset over SF looked promising again today so we went down to the bay to take it in.

An egret walking in the San Francisco Bay with the sunset behind the Golden Gate Bridge

Silhouettes of people by the San Francisco Bay at sunset with the Golden Gate Bridge in the background

San Francisco Bay at sunset with the Golden Gate Bridge

0120

Reposted by Joe Hellerstein

Kelsey Hightower @kelseyhightower.com · 19/11/2024

Just when I thought I've seen it all, a PostgreSQL extension shows up that allows you to embed a SQLite database inside a table. github.com/frectonz/pgl...

Example usage of embedding SQLite inside a Postgres database table.

841030150

Joe Hellerstein @joehellerstein.bsky.social · 01/11/2024

Phil gives big credit to Qizhen Zhang at Toronto for this work. Well done!

010

Joe Hellerstein @joehellerstein.bsky.social · 01/11/2024

This is grownup systems work. Lots of high-level requirements and low-level optimization coming together, with classic hard sw components in between for low latency and high tput (lock-free ring buffers and kernel bypass ftw). More sweat and brains here than many talks I see.

120

Joe Hellerstein @joehellerstein.bsky.social · 01/11/2024

The legendary Phil Bernstein talking @BerkeleySky about his work in sw libraries for DPUs. Phil was paving the way for relational DBs and transactions in the 70s, and is still doing deep, detailed technical work. @Berkeley_EECS @BerkeleyDataSci

Phil Bernstein presenting a slide on DPU networking

140

Joe Hellerstein @joehellerstein.bsky.social · 28/09/2023

Berkeley Data Systems and Foundations (DSF) in the house! With special guests from the awesome Simons Institute semester of database theory (HT NEU db group).

020