This Week’s API Highlights
- Department of Justice in the US Government API category takes the overall title this week with a CASC score of 9.81.
- Department of Justice in the US Government is the fastest API again with a median latency of 49 ms up from 48 ms last week.
- Environmental Systems Research Institute in the US Government API category takes the overall bottom spot again this week with a CASC score of 5.95, down from 6.52 last week.
- We take a good hard look at Microsoft Bing and whether there might be any low-hanging fruit.
Something of interest
Microsoft Bing won the Search API category this week by just 0.02. It’s the slowest API in its category, but it has by far the fewest number of outliers at just 0.12%.
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Microsoft Bing is the fastest from Azure in four out of the six clouds. You want to make the most of home advantage. Being slower than AWS in North America, in particular, is slightly embarrassing.

DNS Lookup Time is always the low hanging fruit in terms of optimizing the performance of your API. If it’s not 4 ms or 12 ms from all cloud locations, there’s something wrong.
Microsoft Bing manages 12 ms from three locations, all Azure (there’s also a 13 ms from AWS East Asia). This is why you need to be actively monitoring your APIs. You need to know what your DNS Lookup Time (and the other latency component) is from the end-user perspectives so that you can proactively ensuring that you are providing an optimal service.
That’s clearly not the case for AWS users in Oceania – or Azure ones in East Asia. There are hundreds of milliseconds of latency to be squeezed out there.

This is no purely theoretical proposition. If Google can do it, Microsoft Bing can do it. Google does indeed have a DNS Lookup Time of 4 ms or 12 ms from all cloud locations. If they can do it, Microsoft Bing can do it.

For AWS North America, it’s the TCP Connection Time and the Handshake Time, meaning that Microsoft Bing APIs are faster from there than from Azure.

That’s 21 ms in extra latency alone from Azure, so plenty of opportunity, once DNS Lookup Time is sorted, to deal with the secondary causes of degraded latency.

API Analysis: Tops in Overall Quality
Week Ending 26 April 2021
Category | Organization | CASC score  |
Corporate  | GitHub | 9.60 |
COVID-19 | WHO | 9.40 |
Search  | Microsoft Bing | 9.32 |
Social Networks  | 9.75 | |
UK Government  | Met Office | 9.00 |
US Government  | Department of Justice | 9.81 |
Messaging APIs  | Slack | 9.38 |
Department of Justice in the US Government category takes the overall title this week with a CASC score of 9.81.
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 three 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 9.32 or more, which is an entirely acceptable level of performance.
API Analysis: Top Performers by Latency
Week Ending 26 April 2021
Category | Organization | Median Latency  |
Corporate  | Google OpenID Connect | 99 ms |
COVID-19 | WHO | 90 ms |
Search  | Duck Duck Go | 124 ms |
Social Networks  | 55 ms | |
UK Government  | Police.UK | 69 ms |
US Government  | Department of Justice | 49 ms |
Messaging APIs  | Slack | 275 ms |
Department of Justice in the US Government is the fastest API again with a median latency of 49 ms up from 48 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 26 April 2021
Category | Organization | CASC score  |
Corporate  | Auth0  | 7.93 |
COVID-19 | 5.37 | |
Search  | Nobody under 9.00! |  |
Social Networks  | Nobody under 8.00!   |  |
UK Government  | NHS | 6.70 |
US Government  | Environmental Systems research Institute  | 5.95 |
Messaging  | Nobody under 8.00!  |  |
Environmental Systems Research Institute in the US Government category takes the overall bottom spot again this week with a CASC score of 5.95, down from 6.52 last week. Three out of the seven categories don’t have an API outside the Green Zone and thus don’t appear in the table, up from two last week. Search has nobody below 9.00.
See you again in a week as we smash into May(!). Don’t forget to look out for our monthly report for March 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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