There’s something we don’t really talk about enough.

Nigeria is connected to some of the most powerful undersea cables ever built:
MainOne, WACS, ACE, Glo-1.
Billions of dollars of infrastructure sitting right off our coastline.

Yet most of my mutuals and I are still buying 1GB for ₦1,000, and it’s finishing in 2 hours.

Something is just so deeply wrong, and most people don’t even know where to point the finger. It’s very easy to assume the problem is the cables, like maybe there isn’t enough international bandwidth coming in.

That’s never been the problem.

The problem starts the moment the signal leaves the water and tries to travel inland. That’s where everything collapses.

Bookmark this tweet right now.

Not after reading. Now.

At some point, you will build a payment system, work on one, or inherit one that is already broken.

When something goes wrong, and it will, you will need exactly what I am about to show you.

This is the most complete payment system breakdown I have ever written.

Every flow. Every edge case. Every trap. One thread In 2023, I built a payment system for a marketplace.

First month: ₦127 million processed.

I was celebrating.

Then my finance person called.

“Stephen, the numbers don’t add up. There’s a ₦4.3 million discrepancy.”

No duplicate charges. No missing webhooks. No obvious bug.

Just ₦4.3 million sitting somewhere between the user’s bank and my merchant wallet.

Unaccounted for.

I aged five years that week.

Let me save you from that. 👇

A startup spent 18 months building a product for Nigeria
launched it, got press, investors were happy, the team was proud
then something happened that nobody in that office saw coming... The first week after launch the numbers looked great
downloads were coming in, signups were going up, everyone was celebrating
then the support messages started
"the app keeps loading" "I can't submit the form" "it just shows blank screen"
the team was confused because on their end everything was working perfectly fine

A Nigerian fintech startup lost ₦47 million in one night.
Not to hackers. Not to fraud.
To one missing line of code.
Every backend dev in Nigeria needs to see this It was 2am. Their support inbox was on fire.
Users calling, screaming, money left their wallets, nothing reached the recipient.
The on-call dev opens the logs and sees thousands of silent failures stretching back to 9pm.
No alert. No rollback. Nothing.

Two years ago, a developer I know launched a small product here in Nigeria.

Everything was going fine.

Users were signing up, logging in, and using the platform daily.

Then one morning he woke up to something strange.

Several users were complaining their accounts had been accessed… without their permission.

Kindly bookmark for yourself and retweet so others too can learn Nothing looked wrong at first.

Passwords weren’t leaked.
Database wasn’t breached.
Servers weren’t compromised.

Yet attackers were somehow acting as legitimate users.

Which raised a bigger question:

If the credentials were safe… how were the attackers getting in?

Last year a junior developer built an app that suddenly went viral.

Everything was working perfectly… until 200,000 users showed up at the same time.

The server crashed.
The database froze.
Users couldn’t log in.
The product died in 6 hours.
Weeks later he interviewed at a big tech company.

They asked him one question:

“How would you design a system that can handle 1 million users?”

He failed the interview.

Not because he couldn’t code.

Because he didn’t understand system design.

This thread will explain system design so simply that when you face this question in an interview, you’ll know exactly what to say.

Bookmark and retweet this. You’ll need it someday. Most developers prepare for interviews by grinding:

• LeetCode
• Algorithms
• Framework questions
But senior engineering interviews often care more about one thing:
Can you design a system that scales?

A friend of mine walked into a backend interview feeling confident.

10 minutes in, the interviewer asked:

“What actually happens when you type a website URL and press Enter?”

He froze.

Not because it was hard… but because nobody ever explained it simply.

So here are backend interview questions explained in plain English.

Bookmark this. Retweet for others preparing. What happens when you type a website URL and press Enter?

Example: google.com

Here’s the simple flow:

• Your browser asks DNS for the website’s IP address
• DNS responds with the server location
• Your browser sends a request to that server
• The server sends back HTML, CSS, and JavaScript
• Your browser renders the webpage

Simple chain:

Name → Address → Request → Response → Page loads.