Messages Need a Protocol Before They Need a Chat UI
A patient taps a kiosk and asks for help. A staff member replies from another screen. The same message may appear in the app, trigger a push notificat…
Testing & QA
⚑ Report a ProblemLatest Testing & QA news from Tech News
All topics
agents
ai
api
architecture
automation
aws
backend
beginners
career
claude
cybersecurity
database
devchallenge
devops
javascript
llm
machinelearning
mcp
opensource
performance
productivity
programming
python
security
showdev
softwareengineering
testing
tutorial
typescript
webdev
Building Production AI Systems(Final)
Designing AI Systems That Outlive Today's Models If there's one lesson this series has taught me, it's this: Don't build your application around a mod…
LLD Data Structures in Design Context: Why HashMaps Feel So Fast — Understanding Performance Without Memorising Big-O
"A HashMap feels fast not because computers became magically faster. It feels fast because the design avoids doing unnecessary work." In the previous …
LLD Data Structures in Design Context: Why Modern Software Needs Fast Lookup Before Anything Else
"The biggest challenge in large software systems isn't storing information. It's finding the right information instantly." By now we've established tw…
The Day the Warehouse Burned: Lessons in Cross-Border System Resilience
A fire in a fulfillment center on the far side of the world. It didn't make headlines. But for a cross-border e-commerce operation， it was a quiet cat…
When to refactor vs rewrite
A decision tree for grown engineers Every engineering team eventually faces the same dramatic sentence. We should just rewrite this. It is usually sai…
Building Microservices Like a Professional: Lessons I Wish I Learned Earlier
If you've ever started a microservices project by splitting a monolith into dozens of tiny services, you've probably experienced this: "We have micros…
I Found the LeetCode for System Design Interview, and It's Awesome
Disclosure: This post includes affiliate links; I may receive compensation if you purchase products or services from the different links provided in t…
The Follow-Up Questions That Decide System Design Interviews (And How to Pre-Empt Them)
Where Interviews Are Actually Won Ask interviewers where candidates separate, and almost none will say "the initial design." Prep materials have conve…
trelix v2.7 to v2.9: The Release Where the Pipeline Itself Became the Product
On 2026-07-09 I shipped trelix v2.7.0. The architecture felt done — seven retrieval legs, a knowledge graph, an agentic loop. Then I opened the GitHub…
The Backend Patterns I Wish I Learned Earlier
When I started building backend systems, I thought becoming a better developer meant learning more technologies. A new framework. A new database. A ne…
Building Reliable Event-Driven Systems: Event Schemas, Versioning, Contract Testing and Events vs Commands (5/5)
In this final article, we're going to explore Production practices 22. Events Are Delivered, Not Guaranteed A common misconception in event-driven arc…
How We Split a Legacy Monolith Into Microservices Without a Single Outage
8 min read · telecom provisioning platform, 30M+ subscribers Most companies avoid migrating their monolith for one reason: they imagine it as a single…
Building Reliable Event-Driven Systems: Event Schemas, Versioning, Contract Testing and Events vs Commands (part-4)
In this article, we're going to explore Contract Testing Contract testing ensures that event contracts remain stable as systems evolve. Producers rece…
System Design - Building an Experiment Service
So I tried to build an experiment service (here's every wrong turn first) Say you run a website and have a hunch a new signup page converts better tha…
LLD Domain Modeling: The Only Cheat Sheet You Actually Need (Interview + Real System Design)
After going through entities, invariants, state machines, aggregates, bounded contexts, and full systems like Ride Sharing, BookMyShow, and Amazon Car…
LLD Domain Modeling: How Real Systems Evolve Over Time (Versioning, Change & Refactoring Reality)
One thing beginner LLD tutorials rarely show is this: real systems never stay in their “initial design”. They evolve constantly: new features get adde…
A Transition Ledger for Debugging a Five-Wave Godot Dungeon Loop
Disclosure: I work with SEELE AI. This article describes a real internal Godot 4.6 Dungeon Master Tycoon prototype; it is not a public playable releas…
Load Balancing: The Neo Way to Dodge Traffic
The Quest Begins (The “Why”) I still remember the night our API started to sputter under a sudden traffic spike. Users were seeing 502 errors, the mon…
Building Reliable Event-Driven Systems: Event Schemas, Versioning, Contract Testing and Events vs Commands (part-2)
This is part-2 of the article series on "Building Reliable Event-Driven Systems". In this article, we're going to explore Event Schemas . 5. Designing…
We hit an at-least-once delivery trap. Here is how we fixed the race conditions.
If you are running an event-driven architecture with message queues like Kafka, you already know the drill, scalability is awesome, but network partit…
Why Early MVPs Fail Before Launch
Most MVPs do not fail because the first version is too small. They fail because the first version is not focused enough. A real MVP is not just a redu…
# The Complete TypeScript Mastery Guide
Learn TypeScript From First Principles to Senior/Staff-Level Production Engineering If you searched for how to learn TypeScript properly — not just th…
Execution Latency in My Polymarket Trading Bot - Sub-Second Trade Execution System Design
Speed on Polymarket is not what I thought it was when I started building this. I assumed faster was always better. Get the signal, fire the order, win…
trelix v1.0 to v2.7: When "It Works" Meets "It Scales"
Twelve days after I shipped trelix v1.0.0, I was staring at a RetrievalConfig object with two conflicting sets of values and no idea which one was act…
Architecting 21-Service E-commerce with Golang & DDD
Answer-first: Migrating an e-commerce monolith to 21+ distributed microservices using Golang & DDD. Explore Kratos architecture, Saga patterns, an…
HTTP/2: The Protocol That Stopped the Connection Explosion
In the previous article , we explored why HTTP/1.1 eventually became a bottleneck. The web had evolved from a collection of simple documents into a pl…
Beyond TTL: Explicit Cache Invalidation
Most engineers default to TTL for cache invalidation. But a simple Time-To-Live guarantees stale reads for a duration, which is unacceptable for criti…
Idempotency in Payment APIs — Not Optional, Not Later
There's a version of this story that plays out at almost every fintech startup I've worked with: the team ships a payment API, it works in testing, it…
Eventual Consistency Is Misunderstood by Most Engineers
I've interviewed dozens of engineers at the senior level. When I ask them to explain eventual consistency, most recite the textbook answer: "data will…