/Deep Dive

Reversing UK Mobile Rail Tickets

tl;dr: "But what data is inside the barcode of a mobile ticket, and how do they work? Could people who aren’t ticket inspectors get the data out of them? It turns out that the answer is a bit more interesting than I initially expected!" The author shows your ticket barcode, which is often written below the code in plain text, might let someone access a surprising amount of detailed tracking information as to where you are and what trains you’re taking.

featured in #387

Asynchronous Computing At Meta: Overview And Learnings

- Sayak Kundu Artem Denisov tl;dr: "We have built a platform for serverless asynchronous computing that is provided as a service for other engineering teams. They register asynchronous functions on the platform and then submit workloads for execution via our SDK. The platform executes these workloads in the background on a large fleet of workers and provides additional capabilities such as load balancing, rate limiting, quota management, downstream protection and many others."

featured in #387

How We Improved DNS Record Build Speed By More Than 4,000x

- Alex Fattouche tl;dr: "Our network now spans over 270 cities in over 100 countries, interconnecting with more than 10,000 networks globally. According to w3 stats, “Cloudflare is used as a DNS server provider by 15.3% of all the websites.” This means we have an enormous responsibility to serve DNS in the fastest and most reliable way possible."

featured in #383

Hello, PNG!

- David Buchanan tl;dr: Davi discusses the mechanics of how PNGs functions:" I'm writing this article to fulfil my role as a PNG evangelist, spreading the joy of good-enough lossless image compression to every corner of the internet... I'll be referencing the Working Draft of the PNG Specification released in October 2022, but every feature I mention here should still be present in the 1.0 spec."

featured in #382

Hello World Under The Microscope

tl;dr: "We will trace the execution path of the "Hello World" micro-program written in Python and run on Windows, starting from a single call to the high-level print function, through the subsequent levels of abstraction of the interpreter, operating system and graphics drivers, and ending with the display of the corresponding pixels on the screen. As it turns out, this path in itself is neither simple nor short, but definitely fascinating."

featured in #359

Rendering Doom With Emojis

- Bruno Croci tl;dr: "Back in 2020, I had an idea of a simple project to render doom using emojis because of some other doom renderer I saw on Twitter. I decided to take it as a weekend project, and although it took me around a week and a lot of bad code, it works and it’s actually pretty interesting. I don’t think anybody wants to play the game like that, but it certainly looks cool."

featured in #359

How To Build A Digital Wallet In Less Than A Day

tl;dr: Building fintech products is hard. But with a few shortcuts, you can build a functional app in less than a day. Download our eBook and learn how to use our simple APIs to launch new products that support multiple payment methods, track and reconciles payments, and record balances in real time.

featured in #358

Turns Are Better Than Radians

- Casey Muratori tl;dr: "I can understand why some people would be worried about making this switch. Even if you believe me that all user-side code multiplies by pi or tau, and all library-side code divides it back out, you still may have that sinking “math class feeling” that you’d be doing something wrong if you stopped using radians."

featured in #355

How To Solve The Sudoku Puzzle With Programming

- Hillel Wayne tl;dr: "Sudoku is an example of a constraint problem. Most “solving sudoku” tutorials use either backtracking or constraint propagation. These same techniques apply to all constraint problems, and since such problems are so widespread, it doesn’t make sense to custom build an algorithm for every single one. Rather, we want general-purpose constraint solvers we can apply to arbitrary problems."

featured in #354

QR Codes

- Dan Hollick tl;dr: "The Quick Response code was invented by a subsidiary of Toyota to track parts across the manufacturing process. Barcodes were proving inadequate - they can only be read at certain angles and didn't store much data relative to their size. The QR code solves those issues and more." Dan dives into how QR codes work. 

featured in #352