This Week’s API Highlights
- Google in the Social Networks API category takes the overall title this week with a CASC score of 9.68.
- Department of Justice in the US Government API category takes the overall title again with a median latency of 47 ms, the same as last week
- Environmental Systems Research Institute in the US Government API category takes the overall bottom spot this week with a CASC score of 6.52.
- We take a good, hard look at what went wrong with Twitter API this week.
Something of interest
Last week, Twitter was riding high with a first-class API CASC score of 9.74, first in the Social Networks API category. This week it is languishing in the doldrums with a CASC score of just 8.27, placing it second from last.
What went wrong?

Last week, it had a 100% pass rate and just 0.30% outliers. This week has a 99.27% pass rate, very far from 5 Nines Telco strength expected of such a crucial piece of web ecosystem, and 4.98% outliers. It is also nearly 17% slower.

A glance at the API Insights table tells us immediately which was the recalcitrant endpoint: Twitter OAuth 1.0 request token.
Above we see the performance affecting outliers for the week beginning 5 April 2021.
And below we see them for the week beginning 12 April 2021. The display has lit up like a Christmas tree!

There was a continuous outage that lasted from 01:11 UTC on 17 April 2021 to 05:15 on 17 April 2021. That’s a major outage, more than four hours. Anyone trying to get a token during that period would have been out of luck.
We also saw quite a few outliers later that day and continuing to 18 April. Not everybody using your service might be calling that endpoint during that time, so only some of your users are going to be adversely affected.
But this is why you should be actively monitoring your APIs. Active monitoring provides a heartbeat.
You can see immediately when your endpoint went down and when it came back. You are not reliant on your users telling you that something has gone wrong. You know straight away and can start fixing things.
A glance at the HTML returned by the HTTP status code 503 Service Temporarily Unavailable response tells us that this wasn’t a planned outage, so let’s hope that not too many people’s days were spoiled!
API Analysis: Tops in Overall Quality
Week Ending 19 April 2021
Category | Organization | CASC score  |
Corporate  | Slack | 9.57 |
COVID-19 | WHO | 9.51 |
Search  | Google | 9.30 |
Social Networks  | 9.68 | |
UK Government  | Met Office | 9.04 |
US Government  | General Services Administration | 9.52 |
Messaging APIs  | Slack | 9.31 |
Google in the Social Networks category takes the overall title this week with a CASC score of 9.68.
When you look at CASC scores you are looking for a ranking of at least 9.00. Even better is if you can achieve a CASC score of 9.50 or better.
We strive to see organizations that achieve CASC scores of 9.50 or better. For this week, that was the case in four of seven API categories. That’s impressive and these organizations should be proud.
Six of the seven API categories are headed by an API with a CASC score of 9.25 or more, which is an entirely acceptable level of performance.
API Analysis: Top Performers by Latency
Week Ending 19 April 2021
Category | Organization | Median Latency  |
Corporate  | Google OpenID Connect | 102 ms |
COVID-19 | WHO | 88 ms |
Search  | Duck Duck Go | 129 ms |
Social Networks  | 59 ms | |
UK Government  | Police.UK | 69 ms |
US Government  | Department of Justice | 48 ms |
Messaging APIs  | Slack | 269 ms |
Department of Justice in the US Government API category takes the overall title again with a median latency of 48 ms, up from 47 ms last week.
One thing that should be considered when looking at API CASC scores. It’s possible for an API to have periods of time when they are very fast but also periods when they are extremely slow. This means that users will very often have a subpar experience.
You don’t want to simply be fast from time to time. You want to be consistently running swiftly. It is not a good idea to rely on your fastest performance. Overall API speed is the real issue.
API Analysis: Worst Quality
Week Ending 19 April 2021
Category | Organization | CASC score  |
Corporate  | Pivotal Tracker  | 7.75 |
COVID-19 | 5.17 | |
Search  | Nobody under 8.00! |  |
Social Networks  | Foursquare  | 7.96 |
UK Government  | NHS | 6.64 |
US Government  | Environmental Systems research Institute  | 6.52 |
Messaging  | Nobody under 8.00!  |  |
Environmental Systems Research Institute in the US Government API category takes the overall bottom spot this week with a CASC score of 6.52. Two out of the seven categories don’t have an API outside the Green Zone and thus don’t appear in the table, the same as last week.
See you again in a week as we plunge into the last full week of April(!). Don’t forget to look out for our monthly API report for March.
We will also be publishing special reports on the State of the APIs in 2020, so that’s something else to look forward to!
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