Every developer building a trading dashboard or a backtesting engine eventually stumbles on the same mismatch: the live price on your screen moved, but your recorded data doesn’t show a trade at that exact level. The culprit is almost always snapshot aggregation. Let's unpack this from a broker’s perspective and get you to a cleaner, tick-by-tick WebSocket pipeline. A snapshot—no matter how freque
You're in another app and there's a timer counting down at the top of your phone. You lock the screen and the same timer is sitting there. You swipe down to the Notification Center and it's there too, still ticking. It looks like a notification, but a notification can't tick. That's a Live Activity. It looks like three different surfaces (Dynamic Island, lock-screen banner, Notification Center ent
Starting September 2026 every B2B invoice in France must be e-invoiced (Peppol/Factur-X). Germany has mandated XRechnung for B2G since 2020. Italy has been on FatturaPA since 2019. Spain's Verifactu rolls out 2025-2026. If you build accounting software, an ERP, or any e-commerce flow that touches EU customers, you'll likely need to validate these invoice formats at some point. The two main open-so
Hello everyone, I'm @xiaoqiangapi, the Chinese teacher who gives apis a "check-up". An article on , my SQL injection, XSS and prompt hijacked, API are blocked off. Let's take a different approach today - ** not attack, test 'resilience' **. Would the API crash if a sudden wave of requests came in, or if someone typed several thousand characters? I'm curious about it. The tools are still the same o
I finished an English series on the way I think ordinary people can start using AI for real work. The point is not to become an AI expert first. The point is to have one place where you can say what you want, give the tool access to the right folder, and check the result. Anything important still needs a human pause: publishing, deleting, paying, or authorizing. My preferred starting point is simp
When building modern applications, one problem shows up everywhere: How do I uniquely identify data across systems? That’s where UUIDs (Universally Unique Identifiers) come in. A UUID is a 128-bit unique identifier used to identify information in distributed systems. Example: 550e8400-e29b-41d4-a716-446655440000 It looks random - and that’s the point. Traditional IDs (like auto-increment integers
I got tired of not knowing why users were dropping off in my app. Heatmaps show you where people click. Analytics show you when they leave. But nothing tells you how they felt while using it. So I built SessionMood API — a REST API that scores user mood in real time based on behavioral events. You send behavioral events from your frontend: fetch("https://session-mood-api-production.up.railway.app/
A lot of online businesses eventually run into the same problem: traditional payment processors don’t always scale well for every type of business model. Over the past months, I’ve been exploring how modern payment infrastructure works, especially from a technical and architectural perspective. This is not a guide or a product pitch — just a breakdown of what I’ve been learning while building and