System Design 101 – Understanding Reliability

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In our last episode, we discussed Availability-the ability of a system to stay up and running, ensuring users can access it whenever they need it. We used Google Search as an example to explain how it achieves 99.999% uptime, meaning it’s almost always available.

Now, let’s dive into Reliability-a concept that ensures systems not only stay up but also work correctly every single time.

What is Reliability?

Imagine you’re using a ride-sharing app like Uber. You request a ride, and the app shows a driver is on the way. But halfway through the trip, the app crashes, and you lose track of your ride. Frustrating, right?

Reliability is about making sure a system performs its intended function correctly and consistently over time. It’s not just about being available; it’s about working as expected every time you use it.

Why is Reliability Important?

Let’s take a real-life example: WhatsApp. WhatsApp is used by billions of people worldwide to send messages, make calls, and share media. Imagine if WhatsApp delivered messages late, sent them to the wrong person, or lost them entirely. Users would lose trust in the app, and its reputation would suffer.

For businesses like WhatsApp, reliability is critical because:

• It builds trust with users.

• It ensures consistent user experiences.

• It prevents costly errors or failures.

How Do Businesses Achieve Reliability?

Here are a few simple strategies businesses use to make their systems reliable:

1. Error Handling: Designing systems to detect and recover from errors gracefully. For example, if a message fails to send, WhatsApp will keep retrying until it succeeds.

2. Testing and Monitoring: Regularly testing the system to catch bugs and monitoring it to detect issues before they affect users.

3. Redundancy: Having backup systems in place to take over if something goes wrong. For example, if one server fails, another one steps in to keep the service running.

4. Consistent Updates: Continuously improving the system to fix bugs, add features, and adapt to new challenges.

Real-Life Example: Gmail

Let’s look at Gmail. Have you ever sent an email and worried it wouldn’t reach the recipient? Probably not. Gmail is designed to be highly reliable. It ensures that every email you send is delivered correctly, stored securely, and accessible whenever you need it.

How does Gmail achieve this?

• It uses redundant servers to store emails, so even if one server fails, your data is safe.

• It constantly monitors its systems to detect and fix issues before they affect users.

• It has robust error-handling mechanisms to ensure emails are delivered, even if there’s a temporary network issue.

This level of reliability is why billions of people trust Gmail with their important communications.

Reliability is the foundation of trust in any system. Whether it’s WhatsApp, Gmail, or your favorite app, users expect it to work correctly every time. Building reliable systems isn’t just about avoiding failures—it’s about creating consistent, dependable experiences that keep users coming back.

In the next episode of our System Design series, we’ll dive into Consistency-what it means for a system to show the same data to all users at the same time. Stay tuned!

Until then, think about this: How would you feel if your favorite app worked sometimes but failed unpredictably? That’s why reliability matters.