A deep dive into the technology behind building Slack. Written by engineers, for engineers passionate about solving complex technical problems.
Visit slack.engineering → RSS feedOn Hacker News Oct 2016 – Jan 2025
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Slack uses PHP for most of its server-side application logic, which is an unusual choice these days. Why did we choose to build a new project in this language? Should you? Most programmers who have only casually used PHP know two things about it: that it is a bad language, which they would never use if…
This story describes the technical details of the problems that caused the Slack downtime on May 12th, 2020. To learn more about the process behind incident response for same outage, read Ryan Katkov’s post, “All Hands on Deck”. On May 12, 2020, Slack had our first significant outage in a long time. We published a…
When Brendan Eich created the very first version of JavaScript for Netscape Navigator 2.0 in merely ten days, it’s likely that he did not expect how far the Slack Desktop App would take his invention: We use one JavaScript code base to build a multi-threaded desktop application, routinely interacting with native code…
For development teams, process can often be antithetical to speed. Ease of deployment and security tend to have an inverse relationship, with some resentment for the security team occasionally mixed in. You may have seen the following tweet: https://twitter.com/petecheslock/status/595617204273618944?lang=en We believe…
Deploys require a careful balance of speed and reliability. At Slack, we value quick iteration, fast feedback loops, and responsiveness to customer feedback. We also have hundreds of engineers who are trying to be as productive as possible. Keeping to these values while growing as a company means continual refinement…
And now we welcome the new year. Full of things that have never been. — Rainer Maria Rilke January 4th 2021 was the first working day of the year for many around the globe, and for most of us at Slack too (except of course for our on-callers and our customer experience team, who never…
By Laura Nolan, with contributions from Glen D. Sanford, Jamie Scheinblum, and Chris Sullivan. Assessing conditions Slack experienced a major incident on February 22 this year, during which time many users were unable to connect to Slack, including the author — which certainly made my role as Incident Commander more…
webpack is a brilliant tool for bundling frontend assets. When things start to slow down, though, its batteries-included nature and the ocean of third-party tooling can make it difficult to optimize. Poor performance is the norm and not the exception. But it doesn’t have to be that way, and so — after many hours of…
On average, 20% of a knowledge worker’s day is spent looking for the information they need to get their work done. If you think about a typical work week, that means an entire day is dedicated to this task! To help our users find more time in their day, the Search, Learning, and Intelligence team set…
Most new things in technology turn out to be fads: patterns of talking and doing that come and go without leaving a permanent mark. Microkernels; EPIC architectures like IA-64; object request brokers; and 1990s’-style neural nets are gone, and will not return. Sorry for the deep throwbacks; only time proves which…
Starting From the Top Imagine joining a new team at a new company and you finally get access to a codebase. Slack iOS Xcode File Hierarchy 2017 Where do you add a source file for your team’s project? Great question. Your new team has three source directories for you to add files to, and oh,…
Update (October 2024): In response to numerous requests from external developers, we have open-sourced a version of our Enzyme to React Testing Library (RTL) conversion tool. You can now find it on npm, along with detailed instructions on how to integrate and use it in your projects. In the world of frontend…
Did you know that ground stations transmit signals to satellites 22,236 miles above the equator in geostationary orbits, and that those signals are then beamed down to the entire North American subcontinent? Satellite radios today serve hundreds of channels across 9,540,000 square miles. Unless you’re working at a…
Recently Slack on the desktop has been going through an awkward adolescence. Instead of flailing limbs and pitch squeaks, ours has manifested in ways rather more grim: inexplicably failing to render content, reloading during common operations, and error screens that aren’t actionable. The only silver lining has been…
Cron scripts are responsible for critical Slack functionality. They ensure reminders execute on time, email notifications are sent, and databases are cleaned up, among other things. Over the years, both the number of cron scripts and the amount of data these scripts process have increased. While generally these cron…
Slack uses PHP for most of its server-side application logic, which is an unusual choice these days. Why did we choose to build a new project in this language? Should you? Most programmers who have only casually used PHP know two things about it: that it is a bad language, which they would never use if…
Artwork courtesy of the Jenkins project. At Slack we manage a sophisticated Jenkins infrastructure to continuously build and test our mobile apps before release. We have hundreds of jobs running in a variety of different environments. One day something very odd happened — our Jenkins UI stopped working although the…
At Slack, customer love is our first priority and accessibility is a core tenet of customer trust. We have our own Slack Accessibility Standards that product teams follow to guarantee their features are compliant with Web Content Accessibility Guidelines (WCAG). Our dedicated accessibility team supports developers in…
For a company like Slack that strives to be as data-driven as possible, understanding how our users use our product is essential. The Data Engineering team at Slack works to provide an ecosystem to help people in the company quickly and easily answer questions about usage, so they can make better and data informed…