Some Thoughs on Systems Design

April 21, 2020 | 2 minute read

The Big Picture: Systems Design Basics - Part 1

While taking an online course on systems design, I learned some cool ideas worth sharing.

Systems Design is About Thinking in Scale

When developing Catoro, I focused a lot on the actual functionality of the application. However, it actually never came to my head thinking questions such as what if I had 100 million total users and 2 million daily users?. How will the design of my backend and deployment be affected by growth?

Systems design focus on distributed systems meaning a a system whose components are located on different networked computers. Some characteristic of such systems include Scalability, Reliability, Availability, Efficiency, and Serviceability/Manageability. There are also strategies of how to assess and design your system for scale.

Capacity Estimation

Lets take our example of Catoro, a coffee cupping app. Coffee cupping must be read heavy, we can assume a 1:50 ratio between read and write.

Traffic, Storage, Bandwidth Estimates If we assume there are 2M new cuppings per month this actually means about 50M readings same month:

2 * 50 => 50M

What about queries per second (QPS)? Roughly ~0.77. So about one new cupping per second!

2M / (3600(secs in hour)* 24hours * 30days) =~ 1

What about reading? Well with our 1:50 ratio it means 50 readings per second.

How about storage?

Let’s assume we’ll store everything for five years. Since we have 2M every month we should expect to store roughly 120M!

2M * 12months * 5years = 120M

What about each particular cupping? Each cupping lets assume is 1KB of information since there are a lot of parameters to track per cupping as well as total score.

Since hour total storage is 120M we should expect roughly 120GB of storage just of cuppings.

120M * 1KB =~ 120GB

Tip: Try this resource for a good byte/kb/gb etc. conversion tool.

Regarding bandwidth of incoming data we should expect roughly 1KB per second as our QPS is 1/s. Read requests about 50KB with our 1:50 ratio.

Road Ahead for SD Explorations

In the next blog post we’ll talk about the Database / Component Design. Tips for DB schema, REST API, Data Partitioning, Load Balancers, Telemetry and Cache.

Stay tuned!