“This One Page Is Amazing!” — The Day I Was Fascinated by a System Architecture Diagram

Following a London-Built System and Discovering Its “Map”

“Wow! I never knew a system architecture diagram could be this fascinating!”

I still remember the moment I thought that.

At the time, I was involved in a project to introduce a system developed in London into Japan.

My main task was translating a large volume of documentation provided by the other side from English into Japanese.

Of course, it was not simply a translation task.

I had to understand the system while translating the documents.

As I continued reading the English documentation, I felt as though I was gradually stepping inside a cutting-edge system.

Translating Documents While Discovering the World of Finance

What was interesting was that there was much more than just system documentation.

The project included a huge amount of business-related documentation as well.

As a result, I began studying not only the system, but also the financial business behind it.

I also studied the Japanese financial business so that I could better understand how the system would be used in Japan.

The knowledge I had gained through several professional certifications also turned out to be surprisingly useful.

“Ah, so this business process is why this system is needed.”

Little by little, the connection between the business and the system began to make sense.

I was supposed to be translating documents, but before I knew it, I was learning about the structure of financial services.

And then I could begin to see how the systems supported that financial business.

It was a remarkably valuable learning experience.

Code, Servers, and More and More Roles

As I dug deeper into the system documentation, I also encountered pieces of code.

There were server architecture diagrams, too.

At first, I thought:

“There are this many servers?”

But when I looked more closely, I realized that each server had a different role.

A server for handling logs.

A server for batch processing.

Servers responsible for individual functions.

Then I suddenly realized something.

“Ah, I see. Rather than building one extremely sophisticated application, they have combined many systems, each with a relatively focused role.”

Each individual system had its own responsibility, and together they formed a much larger service.

Once I understood that concept, the overall architecture gradually became easier to understand.

And Then I Found the “Map” on a Single A3 Sheet

But among all the documents, the one that impressed me the most was the system architecture diagram.

There were countless systems.

There were numerous servers.

And everything was connected in complex ways.

Yet somehow, all of it fit onto a single A3 sheet of paper.

“Wait… all of this is on one page?”

That was my first reaction.

What impressed me even more was that the people on the other side of the project always carried this system architecture diagram with them.

Whenever they needed to check something, they looked at the diagram.

Whenever they explained the system, they referred to the diagram.

It was almost as if they were carrying a map of the entire system with them.

The System Architecture Diagram Was a “Map”

That was when I truly understood the value of a system architecture diagram.

It is not simply a technical document.

It is a map that allows you to see, at a glance:

“Where does each system fit, and what does it do within the overall architecture?”

When you are walking through an unfamiliar city, a map tells you where you are.

It shows you where you want to go.

And it helps you decide which route to take.

A system is much the same.

Even when there are countless systems, having a map that lets you see the entire landscape makes the whole thing easier to understand.

“Especially this system architecture diagram! This is really good!”

That was exactly what I thought.

And from that point on, throughout the project, that single A3 system architecture diagram became the document I referred to the most.

Whenever I didn't understand something, I looked at the map first.

Whenever I learned about a new function, I checked where it belonged on the map.

Whenever I explained something to someone else, I pictured that map in my head.

Looking back, what fascinated me that day was not simply that it was a beautiful diagram.

It was because it organized a complex system into a form that human beings could understand.

In DX, the ability to build systems is important.

But the ability to make complexity visible and understandable is just as important.

That single A3 diagram taught me that.

I can do it! Tomorrow, I’ll take the next step.