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first draft of cdn explainer

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Riordan 9 years ago
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      api-keys-rate-limits.md

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api-keys-rate-limits.md
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@ -1,8 +1,8 @@
# API keys and rate limits # API keys and rate limits
## Obtain an API key ## Get an API key
To use the Mapzen Search service, you must first obtain a free developer API key. Sign in at https://mapzen.com/developers to create and manage your API keys. To use the Mapzen Search service, you must first get a free developer API key. Sign in at https://mapzen.com/developers to create and manage your API keys.
1. Go to https://mapzen.com/developers. 1. Go to https://mapzen.com/developers.
2. Sign in with your GitHub account. If you have not done this before, you need to agree to the terms first. 2. Sign in with your GitHub account. If you have not done this before, you need to agree to the terms first.
@ -10,7 +10,7 @@ To use the Mapzen Search service, you must first obtain a free developer API key
4. Copy the key into your code. 4. Copy the key into your code.
## Rate limits ## Rate limits
Because Mapzen Search is a free, shared service, there are limitations on the numbers of requests to prevent individual users from degrading the overall system performance. Because Mapzen Search is a free, shared service, there are limitations on the numbers of requests to prevent individual users from degrading system performance.
Mapzen Search allows you a maximum of: Mapzen Search allows you a maximum of:
@ -54,17 +54,25 @@ If you exceed your limits, the service will respond with the status code `429 To
``` ```
## Security ## Security
Mapzen Search works over HTTPS, in addition to HTTP. You are strongly encouraged to use HTTPS for all requests, especially for queries involving potentially sensitive information, such as a user's location or search query. Mapzen Search works over HTTPS and HTTP. You are strongly encouraged to use HTTPS for all requests, especially for queries involving potentially sensitive information, such as a user's location or search query.
## Content Delivery Network, Edge Caching, and Rate Limit Count ## Content Delivery Network, Edge Caching, and Rate Limit Count
Mapzen Search uses an "edge cache" in order to serve frequently requested content to our users as quickly as possible. This affects the way we calculate hits against your rate limit, as queries that are served out of the edge cache do not count against your limit of Requests per Second or Requests per Day (though they are reflected in your [Developer's Dashboard](https://mapzen.com/developers/)). Mapzen Search uses an "edge cache" to serve often requested content to our users as quickly as possible. This affects the way we calculate hits against your rate limit, as queries that are served out of the edge cache do not count against your limit of Requests per Second or Requests per Day (though they are reflected in your [Developer's Dashboard](https://mapzen.com/developers/)).
An edge cache (also known as a "Content Delivery Network" or CDN) is a network of computers, geographically spread across the world, designed to shorten the physical distance data must travel from us to you so it can get there faster. If you've ever tried to access a common service on the other side of the world and wondered why its so slow, it's because the physical distance the information must travel is that much further. We use a content delivery network to help alleviate this effect and to limit the impact of common queries on our application servers. An edge cache (also known as a "Content Delivery Network" or CDN) is a network of computers, geographically spread across the world, designed to shorten the physical distance data must travel from us to you so it can get there faster. If you've ever tried to access a common service on the other side of the world and wondered why its so slow, it's because the physical distance the information must travel is that much further. We use a content delivery network to help reduce this effect and to limit the impact of common queries on our application servers.
When you send a request to Mapzen Search, it first goes to the CDN server that is the closest path from your internet service provider before its forwarded onto a Mapzen Search application server (you can see a [map of locations](https://www.fastly.com/network-map) from our CDN, [Fastly](https://www.fastly.com) to see where your requests are likely being sent). If it's the first time that CDN server has seen that request in several days (we update our cache at least once every 7 days), the CDN server then passes your API call on to one of our Mapzen Search application servers. When it comes back with a response to your API call, that nearby CDN server keeps a copy of that response around (minus any personal data to your application, like your API key). If you or another nearby user makes that same API call, you'll likely be sent to the same CDN server, which has kept a copy of the response in its local cache. From our offices in New York, this has the effect of shortening a query to Mapzen Search from 190ms to 21ms. Your speed improvements may vary. When you send a request to Mapzen Search, it first goes to the CDN server that is the closest path from your internet service provider before its forwarded onto a Mapzen Search application server (you can see a [map of locations](https://www.fastly.com/network-map) from our CDN, [Fastly](https://www.fastly.com) to see where your requests are likely being sent). If it's the first time that CDN server has seen that request in several days (we update our cache at least once every 7 days), the CDN server then passes your API call on to one of our Mapzen Search application servers. When it comes back with a response to your API call, that nearby CDN server keeps a copy of that response around (minus any personal data to your application, like your API key). If you or another nearby user makes that same API call, you'll likely be sent to the same CDN server, which has kept a copy of the response in its local cache. From our offices in New York, this has the effect of shortening a query to Mapzen Search from 190ms to 21ms. Your speed improvements may vary. And they may vary from location to location, as requests from different places and different internet providers may be served by different edge cache servers.
What this means is, especially for common queries, like we see on `/autocomplete`, users will get a significant speed boost by sharing [...]. What this means for most users is that for common searches like `/v1/search?text=new york`, there's a good chance your search will come back super-quick, and sometimes, not count against your rate limit. This comes especially in handy with Autocomplete, where many thousands of places all start with the same few root letters (Think `new` as the root of `new york` `newark` `new jersey`). [This would be a great place for a diagram]
Because these cached queries are so much faster and don't increase the impact to our application servers, we do not count them as part of the Unless you've made a particular API call right before, you won't know ahead of time whether it'll be served from the edge cache. But once you make an API call, you can find out quite a bit in the HTTP headers of the response. HTTP headers are part of every request you make on the web, but aren't the core content itself. It's embedded metadata that tells your browser (or other software interpreting the reqest) how to make sense of it.
We will do a "soft purge" of our cache at least once every 7 days as well as after every update to the service (//TODO DO WE DO THIS?). There are two sets of headers that will be extremely helpful here:
The header `X-Cache` will tell you if your request was served from the Mapzen Search application server (`MISS`) or the cache server (`HIT`). This header should be there for any query you make to the Mapzen Search API. Any query with `X-Cache: MISS` is a query that counts against your rate limit.
The headers `X-ApiaxleProxy-Qpd-Left` tells you the number of queries left per day and `X-ApiaxleProxy-Qps-Left` tells you the number of queries left per second. Importantly, these headers are only present on `X-Cache: MISS`es.
In most cases, you should assume the default rate limits of 30,000 per day and 6 queries per seconed apply. But, if you keep track of the number of queries left per day in the `X-ApiaxleProxy-Qpd-Left` header, you can keep track of how many unique queries you can continue to make [this is terrible].
While it is safe to make more than 30,000 queries per day with the help of the cache, please keep to your default per-second rate. This ensures the service can run well for everyone [this is terrible too].

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