How Netflix Taught an LLM to Recommend Movies So That You Keep Watching
In this article, we will look at how GenRec was built.
15 min read
Latest
New writing from 52 engineering newsletters and blogs. Every post opens on its author's own site.
Updated
Wednesday 7 October
Can a Cloud-Native Harness Make Agents Reliable Beyond the Desktop?
Kubernetes co-creators Craig McLuckie and Joe Beda aim to bring agent harnesses fully into the cloud.
6 min read
How to read code
Everyone knows how to read a book. Beginning at the first page, you read each word in order, stopping periodically to think, until you arrive at the last word on the last page. That’s how you read a newspaper article, or a poem, or an email. Why would reading code be any…
6 min read
PlanetScaleSimeon Griggs
What today's software owes to Bronze Age clocks
Admission controls in software determine what does or doesn't happen next, and the most common implementation has ancient roots.
8 min read
Tuesday 6 October
Building Git infrastructure for agent-scale development
We're rebuilding GitHub's Git infrastructure while GitHub keeps running, creating a foundation for agent-scale software development.
8 min read
The keys to the Internet change on October 11. Are you ready?
On October 11, 2026, the DNS root switches to a new key-signing key (KSK-2024). Learn what this means for you, and how RFC 8509 trust anchor sentinels allow you to test whether your DNS resolver is ready for the rollover.
7 min read
Beyond synthetic testing: Capturing and replaying real database workloads at Airbnb
How we capture real production database traffic at Airbnb and replay it offline to load-test, plan capacity, and de-risk upgrades. By: Zuofei Wang, Erluo Li Introduction At Airbnb, MySQL-compatible databases are a critical backbone of our online database infrastructure: a fleet…
9 min read
The state of the tech industry in 2026
A look into what has changed, what’s still the same – and what’s broken – in the tech industry. The full video and the summary of my keynote at LDX3 New York
22 min read
Metrics Board: Building an Agent-ready Metrics Layer
Michele Ceccacci; Software Engineer I | Jason Coffman; Sr. Software Engineer | Colm O’Shaughnessy; Software Engineer II | Laura Palmer; Staff Product Manager | Adam Podraza; Manager, Engineering | Surya Karri; Manager, Engineering At Pinterest, reliable and trustworthy metrics…
10 min read
NTS: Authenticated Time at Meta
Meta’s public time service now speaks NTS (Network Time Security, RFC 8915) at nts.meta.com. Packets are authenticated, so a device can verify the time came from us and was not modified on the way. Our NTS servers hold no per-client state. Cookie keys are derived, not stored and…
11 min read
Why LLMs Agree With You Even When You’re Wrong
When LLMs sometimes agree with incorrect claims, it is mostly because their training rewards such behaviour. This reward system is built on several things at once, such as accuracy, helpfulness, politeness, and responses that people like.
12 min read
12 things I miss since coding died
The satisfaction of debugging, rabbit holes, and 10 more
8 min read
Smarter personalization: How property data helps us understand user price sensitivity
Introduction Existing systems estimate user price sensitivity primarily from spending behavior or demographic proxies. They do not systematically account for residential property values, which can indicate a user’s financial circumstances. This omission creates three…
What is Codemode
More than a year ago I wrote a few posts here that recommended people not to load custom tools into their context (or MCP servers) but to just use more scripts. Most importantly I wrote that Code Is All You Need and I wrote about that MCP needs code. With Pi 1.0 we now added MCP…
12 min read
Building and testing a config management orchestrator for Windows
The following is part of a series of posts about 2026 summer intern projects—for more, see “What the interns have wrought, special jumbo 2026 edition”
PlanetScaleEtienne Berube
Introducing Dedicated Read Replicas for Postgres
Use dedicated read replicas to isolate read-only workloads and distribute your data across data centers around the world.
1 min read
Monday 5 October
Lessons From 4 Years of Writing the Engineering Leadership Newsletter
How I started with the newsletter, the most important lessons and what I would tell myself 4 years ago!
9 min read
The LLM Blindspot: Why Models Forget What’s in the Middle of Your Prompt
In this article, we’ll look at why LLMs have this bias against middle information.
11 min read
64 AI Concepts Every Software Engineer Should Know
#187: Part 1 - Generative AI, RAG, AI Agents, and 14 others.
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Neetcode: Google vs Amazon, Programming Interviews, Quitting Big Tech
Neetcode is the most well-known coding interview prep creator with over 1M+ subs on YouTube.
Podcast
Everything we launched during Birthday Week 2026
We celebrated our 16th birthday with 46 announcements across open source, post-quantum security, AI agents, and developer platform upgrades. Here’s a day-by-day roundup of everything we shipped.
9 min read
One year later: the power of 1.1.1.1 interns
A year after announcing our goal to hire 1,111 interns, more than 750 early-career builders have shipped real products across 48 teams at Cloudflare. From Birthday Week launches to post-quantum security, our interns prove that AI amplifies human potential instead of replacing it.
4 min read
Before You Build, Ask Yourself: Who is Your Bullseye Customer?
A shared customer hypothesis can resolve decisions that a month of roadmap debate can’t.
5 min read
Fragments: October 4
In response to my last fragments (probably the bit about us worrying if LLMs have consciousness when we when we should be wondering why they don’t have a conscience) “Metalanguage” replied: we shipped the id and forgot the superego. classic software lifecycle. I don’t know what…
7 min read
Benchmark In Milliseconds
How long should a micro benchmark run? My rule of thumb is to tweak the input size until the benchmark takes about 300ms, for the following reasons:
Scaling and benchmarking a critical message bus using a new indexing strategy
The following is part of a series of posts about 2026 summer intern projects—for more, see “What the interns have wrought, special jumbo 2026 edition”
Powering AI-led research through simulation
The short story Consider a Friday evening. A food order arrives from a mall in the city center. One driver is nearby; another is finishing a drop-off and will be available shortly; a second order from the same mall may or may not appear in the next two minutes. Dispatch the…
Sunday 4 October
Arc Notes Weekly #108: What’s Worth Building
Cheaper intelligence, faster interfaces, and the judgment needed to turn agent work into useful software.
3 min read
How Vector Database Search Billions of Vectors in Milliseconds
#186: Understand HNSW Graphs, Approximate Nearest Neighbor Search, and Key Parameters Engineers Tune in Production
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Before You Buy Another AI Subscription
Open-source alternatives across 19 workflows, from coding to voice. Choose your tools, bring your model, and know when to keep paying.
15 min read
Strands Decider: Why Not an Encoder?
Strands Decider: Why Not an Encoder? Expertise level: exhausted. As I admitted in my last post, I am very much not an expert model developer. What follows is likely to be, at least partially, inaccurate. I have tried to be careful and quantitative, to partially balance a lack of…
How to Solve: AAC Heavyweight M1 (Savage)
FFXIV raid mechanics explained in plain language.
16 min read
Saturday 3 October
We're going to need default hard budget caps on pretty much everything
Here's a product feature which the world is going to need a whole lot more of over the coming months and years: default hard budget caps. I'm talking about the feature of pay-by-usage services and APIs that lets you say "after $X/month, cut this thing off and return errors"…
Superpersuasion will look like bribery
The idea of “superpersuasion” has been floating around the AI safety community for decades. Now that powerful and difficult-to-control LLMs have appeared, people are again talking about the idea that a sufficiently intelligent AI might be able to persuade people to do whatever…
4 min read
Shipping is the foundation
There are lots of skills involved in being a successful engineer at a big tech company. Running effective meetings, writing good design docs, fleshing out tickets and epics, improving team processes, tech leading small groups of engineers, and so on. But all of these rest on the…
4 min read
Friday 2 October
How to Develop a Proactive Mindset as an Engineer
An adapted chapter from my upcoming book “The Multiplier Mindset”, published by O’Reilly.
Paid
Refactoring Street Fighter With AI 🕹️ — with Adam Tornhill
Watch now (54 mins) | Refactoring Podcast • Episode 73
PaidPodcast
How recurring network maintenance exposed 6 bugs
Jane Street does a lot of network maintenance over the weekends. In each maintenance, a cabinet may lose connectivity for 15 to 25 minutes. Our internal Kafka infrastructure is supposed to be resilient to these partitions, and reconnect when connectivity resumes. For several…
Thursday 1 October
The Pulse: Firebase’s global outage & poor response
Also: OpenAI’s platform play that has similarities to AWS, more data on companies moving to open models, and more
Paid
ShopGym: Realistic, reproducible sandboxes for shopping agents
ShopGym creates realistic online stores and generates shopping tasks based on each store’s products and features. Developers can then repeatedly test shopping agents under consistent conditions.
When Building Gets Easy, Who Holds It All Together?
10 reads on the human work that holds engineering teams together
7 min read
PlanetScaleDirkjan Bussink
Designing Neki for performance
How Neki only decodes the parts of a PostgreSQL result the router actually needs.
15 min read
How we extended Apache DataFusion to execute one query across many machines
Learn how Datadog built Distributed DataFusion to scale interactive Apache DataFusion queries across multiple machines.
Wednesday 30 September
Distributed databases with Peter Mattis
Cockroach Labs co-founder Peter Mattis discusses building reliable distributed systems and how AI helps him write more code without sacrificing quality.
Podcast
Principles for effective slides
Not every presentation needs slides, but when they earn their place, they work as a visual channel that complements the speaker rather than replacing them. Sumeet Gayathri Moghe sets out the principles that follow from that idea — control over the rate of knowledge exposition…
How we built an async-aware Python profiler
Learn how we made Python profiling async-aware while reducing profiler overhead and preserving context across asyncio tasks.
Tuesday 29 September
Personalization without user identity
How Airbnb uses proximity signals to personalize without relying on individual user history. By: Wei Jiang, Bin Xu, Bharathi Thangamani, Weiwei Guo, Sundar Srinivasavaradhan, Tracy Yu, Huiji Gao, Swapnil Ghike, Michael Kinoti Great personalization starts with knowing your user…
6 min read
OpenAI DevDay 2026 live blog
I'm at OpenAI DevDay today, in Fort Mason, San Francisco. Same as last year I'll be live blogging the keynote and some other notes during the day. OpenAI gave me a free ticket and a seat in the "creator" area for the keynote. You are only seeing the long-form articles from my…
Bliki: Sensible Default
A Sensible Default is a practice that, absent some overriding context, should be used when carrying out a certain kind of task. In software development such sensible defaults might include things like “use version control”, “separate UI logic from domain logic”, “automate…
2 min read
Mathematicians, Here’s a Way To Think About Your Existential Crisis
Two years ago programmers were all like, “What I do is code.
2 min read
Code as CraftEmily Sommer
That Which We CAN Do: Sustainability in a World of AI
As computing use grows, so does its environmental footprint. While hardware and software have become significantly more efficient, AI demand is growing even faster, outpacing those efficiency gains and increasing the overall environmental impact of computing. What’s more…
10 min read
Dropbox TechGreg Unrein and 2 others
Evolving our calendar assistant Reclaim to be AI-native without starting over
How we redesigned Reclaim for AI and natural-language requests while preserving the scheduling experience people rely on.
7 min read
Language Models for Text Classification: From Bag-of-Words to Jev
A Visual Guide to RNNs, CNNs, Transformers, and Calibration, with Hands-On Experiments on Accuracy and Efficiency
33 min read
Deser: Rethinking Rust Serialization
Serde is an amazing serialization library for Rust and it has been a huge reason why I felt productive with it for years. However already while at Sentry I got quite frustrated with some of the limitations with it but actually replacing Serde is tricky because of the might that…
13 min read
Monday 28 September
The Code Nobody Reads
Line-by-line review is going away. Whatever replaces it has to earn the trust reading used to provide.
18 min read
Amazon VP: Questions On Corporate Politics But They Get Increasingly Darker | Ethan Evans
In this episode, I asked Ethan Evans (ex-Amazon VP) question about common situations in corporate politics but they get increasingly dark.
Podcast
Don’t Mistake Friendliness For Friendship
Being close to your team and being their manager are not the same, and the two run on different rules.
6 min read
Small Decisions: Engineering a Leading Model
Small Decisions: Engineering a Leading Model Or trying to, at least. Update: An evolved version of the model described here is now available as part of Strands. Check out strands-decider on github and HuggingFace. My day job has been primarily in AI for three years now, but I’d…
Sunday 27 September
2026 in LLMs (so far)
On Friday I gave the closing keynote at the WeAreDevelopers World Congress North America in San Jose. I tied together the key trends from the past year into a chronological exploration of everything that happened in 2026. The video is on YouTube; here are my annotated slides and…
Arc Notes Weekly #107: Closing the Loop
Cloudflare’s 100TB RAM saving, faster Postgres analytics, and keeping humans in the loop as agents take on more work.
3 min read
How Companies Assess Fit of Engineers on a Behavioral Interview
The 4 dimensions that determine your level of your offer.
14 min read
Become an AI-Second Engineer
Everyone can generate code. Trusted engineers know what’s worth shipping, and use AI and mentors to build that judgment.
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Replacing the old battery on rechargeable bike lights
Hello! Recently I needed bike lights for my bike. And I remembered that I already had rechargeable bike lights that I bought ten years ago, that I hadn’t tried in a long time. I tried to recharge them, but after fully charging them, they only worked for maybe 5 minutes before…
5 min read
Saturday 26 September
Friday 25 September
Trading a Cloud Identity for Your Own: Workload Attestation on Managed Compute
By Dhruv Pratap Introduction Organizations that have been around for a while usually run two identity systems side by side. One belongs to the cloud provider: IAM roles, instance profiles, execution roles. The other is your own, and it is the one your internal services actually…
8 min read
Partition Finalization in Pinterest’s Next-Generation DB Ingestion Framework
Qianrui Zhang | Sr Software Engineer, Logging Platform Kanchi Masalia | Software Engineer II, Stream Processing Platform Liang Mou | Sr Staff Software Engineer, Logging Platform Yi Pan | Principal Engineer, Agent Platform Introduction This is the third post in our series on…
10 min read
Improving site performance by shipping more CSS
How we fully migrated github.com away from CSS-in-JS.
7 min read
Automated merchant review summary system with integrated feedback
Introduction Merchant reviews contain useful details about food quality, portion size, packaging, and value. Finding these details often requires reading many comments. Aggregate ratings simplify comparisons, but they do not explain what shaped each score. We built the Automated…
Thursday 24 September
Bringing Private Processing to Meta AI Glasses
We believe glasses are the best form factor for having AI help throughout your day. They can understand your personal context better than other kinds of devices and keep you present without picking up a mobile phone. Most of the time, glasses are helping you see well, protecting…
10 min read
Wednesday 23 September
What Happens When the Model Eats the Stack? Rethinking the Research Agenda for Data Agents to Withstand the Bitter Lesson
General methods that scale with computation will inevitably displace hand-engineered domain knowledge! Sutton’s Bitter Lesson hangs like a Sword of Damocles over all of us. This paper, which just dropped, applies that lesson to data agents, and says that as LLMs improve, they…
6 min read
