在 Hacker News Daily 上看到拿 Cloudflare Workers 跑 Geolocation API：「How to make simple Geolocation service」。
作者想要做一個很簡單的 Geolocation API，一開始的想法是在 AWS Lambda 上用 MaxMind 的資料，但 latency 偏高：
However, I quickly realized that the response time isn't what I've expected - on average the response took somewhere between from 200ms to 500ms. So I started looking for other options.
所以作者就想到是不是有有機會丟到 Cloudflare Workers 上，但發現 license 看起來是個問題，另外因為把 MaxMind 的資料庫丟進去，會超過 worker 的時間限制：
And for this case MaxMind offers GeoLite2 database, however you'll be in charge of hosting this database on your server and making regular updates of the database. You also need to make sure your project is compliant with MaxMind's License.
However, this solution had one really big caveat - MaxMind GeoLite2 database does not work on Cloudflare Workers due to some runtime limitations.
結果作者後來發現 Cloudflare Workers 上本身就會帶 Geoloation 資訊了，不需要另外拉 MaxMind 的資料查：
And after exploring their documentation, I realized that the Request object in function have an access to cf object, which contains some useful information about the visitor, including visitor's country!
另外我翻了一下價錢，主要是算次數的，看起來 Free Plan 就可以 100K/day (執行時間限制是 10ms)，而如果是付費方案的話則是 USD$0.5/M (50ms)，這樣對一些小專案來說，Free Plan 似乎是夠用了...