I’m a big fan of this Napkin Math newsletter. If you haven’t subscribe to Napkin Math, you should do it. In this edition of Napkin Math, we’ll invoke the spirit of the Napkin Math series to establish a mental model for how a neural network works by building one from scratch. In a future issue we will do napkin math on performance, as establishing the first-principle understanding is plenty of ground to cover for today!

How to approach design a system at a scale of WhatsApp. What is data storage, push notification, user status all look like. What is the plan of monitoring and identify bottle neck.

JPEG (or JPG) is not really a file format but rather an image compression standard. The JPEG standard is complicated with many different options and color space regulations. It was not widely adopted. A much simpler standard version was advocated at the same time, called JFIF. This is the image compression algorithm that most people mean when they say JPEG compression, and the one that we will be describing in this class. Note that the file extensions .jpeg and .jpg have stuck, even though the underneath algorithm is (strictly speaking) JFIF compression.

On September 30th 2021, Slack had an outage that impacted less than 1% of our online user base, and lasted for 24 hours. This outage was the result of our attempt to enable DNSSEC — an extension intended to secure the DNS protocol, required for FedRAMP Moderate — but which ultimately led to a series of unfortunate events.

As part of Uber engineering’s wide efforts to reach profitability, recently our team was focused on reducing cost of compute capacity by improving efficiency. Some of the most impactful work was around GOGC optimization. In this blog we want to share our experience with a highly effective, low-risk, large-scale, semi-automated Go GC tuning mechanism. If you are into Go and memory managemet, checkout Saving a Third of Our Memory by Re-ordering Go Struct Fields too.

It’s 2022 and the dominant way of handling user input is still based on events and — in some form or another — callbacks. But in nearly every code base I’ve worked in, the hairiest, most difficult-to-modify logic is in the event handling code. To help me understand the pros and cons of the events-and-callbacks model and to experiment with some other approaches, I decided to write up a simple example in a three different styles.

UUID has a string reperesentation which make it looks like string with non numeric character, but behind the scene, many system store them as a 128 bit number.

new year, learn something new, do something different, take on challenges. The author will be building an SQL query which will emulate a quantum computer. This query will process quantum assembly, build the circuit, run the emulation and make the measurements.

ssh-agent forwarding allow remote host to forward authentication to a local node. It’s very useful when you do a ssh-add, then login to remote server, and you can use your key to login to another server. but it open a hole where anyone can use it to connect to any host with your keys. A recent experimental feature for the upcoming OpenSSH 8.9 release will help close that hole. Instead of allowing the keys held in the agent to be used for authenticating to any host where they might work, SSH agent restriction will allow users to specify where and how those keys can be used.