Two people edit the same document at the same time from two devices, offline, and when they finally reconnect the result is not a tangle of broken cells or a blunt “last writer wins”: both...
When you open a complex application in your browser, most of the time JavaScript handles everything. But a format arrived to make sure that is not the only language your browser understands: WebAssemb...
You ask the disk to write a few bytes in a specific place, and you believe that is exactly what it does. In an SSD (solid-state drive, storage without moving parts that uses flash memory) that belief ...
Your program creates objects endlessly: a list here, a string there, a temporary user. Each one occupies a corner of memory. And when you stop using it, it would stay there forever, piling up until th...
Almost everyone believes that digitally signing is encrypting the message so nobody can read it. It is not. They are two cousins that often get confused: encryption seeks secrecy; signing seeks what a...
Some operations in memory are astonishingly elegant. One of them is answering, almost for free, a question that at first glance seems expensive: “Is this item in this set?”. For that task ...
Before your browser loads this page —or any site with a padlock— a silent conversation takes place in a few milliseconds. It is the TLS handshake (TLS, Transport Layer Security: the protocol that encr...
Almost everything that holds your data today lives on more than one machine at once. And the moment several machines appear, an uncomfortable problem shows up too: they disagree. One server says the c...
Every running program believes it owns all of the machine’s memory for itself. That is not a marketing trick: this “illusion” is virtual memory, and without it modern operating syste...
You run SELECT * FROM pedidos WHERE cliente_id = 2421 and, depending on the table, the answer takes an instant or several seconds. The only meaningful difference between the two cases is usually a str...
You have an 800-page novel in front of you. You compress it with gzip and it takes up a quarter of the space. Not a single letter has disappeared: decompressing returns the exact text. What actually h...
Every time you open a large app, you are not connecting to a single machine but to hundreds of servers sharing the load. For your session and your data to always appear where they belong, those machin...
When a graphics chip (GPU) runs a program, it does not do exactly what a CPU does but faster. It does something qualitatively different: it duplicates one thread of execution hundreds of times and lau...
Picture a spreadsheet open to a hundred people at once: everyone reads, one writes, and nobody loses their work. At the scale of millions of transactions per second in a real database, that is called ...
When you type a ñ on your phone, the keyboard does not store the letter: it stores a number. And that number does not necessarily fit in a single byte (a unit of 8 bits, the smallest block a computer ...
We have all experienced it: a download that raced along suddenly slows to a trickle. The more people connect, the worse everything seems to run. That behaviour is not a fault in your provider: it is t...
There is a myth that has circulated since the early days of the SSD: that writing a lot “wears out” the drive and it will die within a couple of years. The truth is far more interesting. A...
When you save a document, your disk does not archive it as a single whole. It chops it into thousands of pieces and scatters them across the surface of the magnetic platter (or across the flash-memory...
Between the moment you press the power button and your desktop appears there is no magic: there is a chain of checks in which every link distrusts the next one before letting it carry on. That ritual ...
The password has been the weakest link in digital security for decades: it gets guessed, leaked, reused and impersonated. Against that hole come passkeys and the WebAuthn standard, which replace the &...
That the web seems faster is not only thanks to fiber optics. Much of the credit belongs to a protocol born a decade ago with an idea that was uncomfortable for the standards of the time: ditching the...
When you ask a language model to retrieve «the most similar thing» to a question, it does not open a normal database and search word by word. It does something stranger: it turns every text into a lis...
When your website takes half a second, it is almost never the fault of a single server. It is the sum of twenty microservices passing the request along like a relay baton, each adding its own millisec...
If you have ever watched two people type into the same Google Doc, Notion board or Figma file at once without the text tearing apart, you were witnessing a distributed-computing problem that took deca...
Opening dozens of browser tabs without a thought for RAM, creating lists, dictionaries or objects and then forgetting about them: almost no programmer worries today about freeing memory manually. That...
When you run an SQL query and the database answers in milliseconds, almost nobody stops to think that the heavy lifting is not done by the table: it is done by an auxiliary structure called an index. ...
When you open a page that runs WebAssembly (or Wasm), the browser is not executing JavaScript that somehow works magic: it is running a binary compiled beforehand, on another machine, inside a virtual...
When you open a website with a padlock, your browser and the server do not just greet each other: they run a three-message cryptographic choreography that decides, in milliseconds, which algorithm wil...
Look at your phone’s clock icon, a WhatsApp notification, music playing, a browser with twenty tabs and an antivirus scanning in the background: everything “at once”. Yet each core (...
The short answer is yes, and the name of that possibility is eBPF (extended Berkeley Packet Filter). Even though the name smells like the packet filtering of the 1990s, eBPF has become the infrastruct...