“The most scalable systems don’t constantly ask what’s happening. They simply react when something happens.” Imagine you’re building an online marketplace. A customer places an order. At first...

“The way you write data isn’t always the best way to read it.” Imagine you’re building an online marketplace. Every day, thousands of customers browse products, place orders, track deliveries,...

“A transaction can roll back one database. A Saga coordinates many databases that have never even met.” Imagine you’re building an online marketplace. A customer clicks Place Order, expecting ...

“A database transaction can guarantee your data is correct. It cannot guarantee the rest of your system knows about it.” Imagine you’re building an e-commerce platform. A customer places an or...

Now that we understand how distributed locks work conceptually, the next question becomes: Where do these locks actually live? Unlike database transactions, distributed locks cannot rely on t...

“Database locks protect rows. Distributed locks protect systems.” Imagine your application has been wildly successful. What started as a simple web application running on a single server now r...

Understanding the Four SQL Isolation Levels Now that we’ve seen the kinds of problems concurrent transactions can create, the next question is obvious: How does a database prevent them? The answ...

“Transactions guarantee that your work completes correctly. Isolation levels determine what everyone else is allowed to see while that work is happening.” In the previous article, we explored...

“Transactions are not just a database feature—they’re one of the fundamental building blocks of reliable software.” Imagine you’re transferring KES 10,000 from your savings account to a friend...

Imagine you’re trying to buy the last ticket for your favorite concert. The website shows: Only 1 ticket remaining. At exactly the same moment, someone else clicks Buy. Both of you complete...