API.expert Weekly API Analysis: Messaging APIs

This Week’s API Highlights

• GOV.UK in the UK Government category and Department of Justice in the US Government category share the honors for the overall title this week with a CASC score of 9.86 the same as GOV.UK last week.
• Department of Justice in the US Government takes the overall title again with a median latency of 48 ms, the same as last week.
• Coronavirus COVID19 API (covid19api.com) in the Covid-19 category takes the overall Wooden Spoon again this week with a CASC score of 4.02 up from 3.88 last week.
• We take a look at the Messaging APIs category and how outliers can impact API performance.

Something of interest

Messaging APIs is a pretty competitive category. All 9 APIs are in the Green Zone, which is good, although only two have a CASC score of 9.00 or over, with Zoom topping the table with a CASC score of 9.16, the lowest among table-topping APIs this week.

We have arranged the table by descending number of outliers. Twilio has the most at 4.93% and, as you can see it is lit up like a Christmas tree. 13 March looks a bad day for outliers, but they are spread through the week.

Twilio has a 100% pass rate, so these are just slow calls that pass. The Twilio endpoint we monitor sends an SMS.

You could argue that SMS is a best-effort service. The message gets there when it gets there. It will usually be pretty quick, but if it gets delayed because of exceptional latency at the API endpoint, so it goes.

Don’t use SMS for time-critical communications.

Of course, how long the SMS takes to get to its destination will depend on the mobile network and that might be the rate-determining component (we don’t measure that because it is not directly related to the performance of the API), but adding, in nearly 5% of calls, tens of seconds on latency on to the time it takes for the text to be received because of the API is not ideal.

This kind of behavior can easily have a big impact on user experience.

Cisco WebEx Teams is offers a stark contrast. Of the six Cisco Webex Teams endpoints we monitor, three had no outliers at all last week. The most is with the List Rooms endpoint at 1.6% and as you can see the endpoint simply isn’t impacting in the same way as Twilio.

Note that both APIs have the same CASC score. The Cisco WebEx Teams List Rooms endpoint is the worst performing endpoint in the category, so it is dragging down Cisco WebEx Teams overall. The endpoint is slow as well as having some outliers, so speeding it and reducing the outliers will improve its quality.

This is why you need to be monitoring your APIs actively. You need to understand how the different aspects of API performance are affecting user quality so that you can address any issues proactively before your clients are affected. And outliers can seem unimportant. If 5% of calls are slow, but still getting through, does that really matter? It will depend, of course, but the extra latency might cause an application that uses the API to time. There can be an avalanche effect that you are not even aware of, but that you will be blamed for when the user finds it is the caused by API outliers.

That’s why you have to know your API to be able to squeeze out every last drop of performance.

API Analysis: Top Performers by Latency

Week Ending 1 March 2021

Category	Organization	CASC score
Corporate Infrastructure	GitHub	9.62
COVID-19	WHO	9.49
Search	Google	9.54
Social Networks	Google	9.67
UK Government	GOV.UK	9.86
US Government	Department of Justice	9.86
Messaging APIs	Zoom	9.16

GOV.UK in the UK Government API category shares the overall title this week with Department of Justice in the US Government API category both with a CASC score of 9.86, the same as GOV.UK last week. A CASC score of over 9.00 is very good and one of 9.50 or more exceptional. Five of the seven categories are headed by organizations with a CASC score of 9.50 or more this week, the same as last week. Sustaining a CASC score of >9.25 over a period of several weeks is a good showing and congratulations to those organizations that achieved it. This week, six of the seven API categories are topped by an API with a CASC score of 9.27 or more.

API Analysis: Top Performers by Latency

Week Ending 15 March 2021

Category	Organization	Median Latency
Corporate Infrastructure	Microsoft Office	220 ms
COVID-19	WHO	85 ms
Search	Google	389 ms
Social Networks	Google	55 ms
UK Government	Police.UK	83 ms
US Government	Department of Justice	48 ms
Messaging APIs	Slack	263 ms

Department of Justice in the US Government takes the overall title again with a median latency of 48 ms, the same as last week. An important caveat: medians can be misleading! An API might have a fast median latency but produce many slow outliers. These won’t affect the median, but they mean that users can experience many calls that were unacceptably slow. So just being fast isn’t everything. You have to be reliable too if you want to have good APIs and get a high CASC score!

API Analysis: Worst Quality

Week Ending 15 March 2021

Category	Organization	CASC score
Corporate Infrastructure	Nobody under 8.00!
COVID-19	covid19api.com	4.02
Search	Nobody under 8.00!
Social Networks	Nobody under 8.00!
UK Government	NHS	6.17
US Government	NASA	6.84
Messaging	Nobody under 8.00!	7.79

Coronavirus COVID19 API (covid19api.com) in the Covid-19 category takes the overall Wooden Spoon this week with a CASC score of 4.02. Four out of the seven categories don’t have an API that appears in the list because there is no API in that category outside the Green Zone, up from two last week. See you again in a week as we plunge even deeper into March (still two weeks to go though!). Also don’t forget to look out for our monthly report for February and the weekly and monthly financial API reports. We will also be publishing special reports on the State of the APIs in the 2020, so that’s something else to look forward to!

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