Docs for Estimating Costs (#633)

* Estimating Costs (WIP)

* cleaned up some of the math

* remove decimals in wide estimates

* remove assumption of where costs will come frome

* correct calculation for network

* links don't work in notes

* Clarify based on comments

docs/_data/navigation.yml

@@ -11,6 +11,8 @@ docs:
  url: /getting-started/publishing-temporary-exposure-keys
  - title: How to Download Keys
  url: /getting-started/downloading-export-batches-keys
+ - title: Estimating the Cost of Deployment
+ url: /getting-started/estimating-costs
  - title: Design
  children:
  - title: Server Deployment Options

docs/getting-started/estimating-costs.md

@@ -0,0 +1,138 @@
+---
+layout: default
+---
+# Estimating costs of hosting the Exposure Notifications Server
+
+ NOTE: This is for informational purposes only. This doesn't account for all
+ costs of operating. This document should be used to assist in understanding
+ how to calculate the cost of deploying this service, not to make
+ budgetary decisions.
+
+This page outlines how you might estimate the cost of deploying the reference
+server for your application. Cost estimates assume the use of Google Cloud,
+deployment and use within the US, and uses the
+[published pricing rates](https://cloud.google.com/pricing) to arrivea at the
+estimation. This could be repeated for other regions as well as for other
+cloud providers. Please note that for much of this simplifications have been
+made. Due to a majority of the expected costs to be incurred due to storage
+serving. 
+
+# Calculating the overall cost
+There are a number of variables that need to be figured out to determine cost.
+
+Let's assume that we are calculating the cost of operating for an area with:
+
+* A population of 10 Million (10,000,000) people. 
+* An exposure window of 14 days
+* 50% adoption of an exposure notifications system
+* 1,250 new cases daily (approximately .01% new cases per day)
+
+From which we can derive:
+* Each new set of keys is 448 bytes (14 days * 32 bytes)
+* Each daily batch is 1,250 * 448 bytes = .56 MB
+* That file is downloaded 5 Million times per day, for (2.8 TB/day downloaded),
+ 84 TB monthly.
+
+# Cloud Components and Pricing
+Due to pricing varying by region, and much of this being scalable, we avoid
+speaking about exact pricing for most of it, instead trying to quantify the
+magnitude.
+
+To have an idea of the deployment size, this document assumes the defaults
+configured for Terraform in
+[vars.tf](https:/google/exposure-notifications-server/blob/master/terraform/vars.tf).
+
+The largest cost is likely to be in Network Egress. In this calculation we
+assume that [Google Cloud CDN](https://cloud.google.com/cdn) is not used but
+instead a [Google Cloud Storage](https://cloud.google.com/storage) bucket is
+read directly. Please note that using Google Cloud CDN will likely result in
+lower cost.
+
+## Cloud Run Costs
+https://cloud.google.com/run/pricing
+
+There are multiple containers needed for a complete deployment: 
+
+* Export Cleanup
+* Exposure Cleanup
+* Export 
+* Exposure
+* Federation In
+* Federation Out
+
+Most of the services run periodically, not constantly. For this reason it is
+likely no higher than 6 containers at this scale. Likely, estimating as if 3-4
+of these containers would get a reasonable upper limit. The resource limits of
+a container are specified in the
+[terraform resource limits](https:/google/exposure-notifications-server/blob/master/terraform/service_federationin.tf#L63)
+as 2 CPU and 1G memory per container.
+
+**Projected Monthly Cost: $500 - $750**
+
+## SQL Database Costs
+https://cloud.google.com/sql/pricing
+
+The default size for SQL Database is configured to:
+* 8 vCPU
+* 30720 MB Memory
+* 256 GB SSD
+
+The cost of this component can vary greatly on the scale is configured to.
+Depending on the needed scale of your deployment this could require a different
+configuration.
+
+For instance, while the default is `db-custom-8-30720`, the documentation
+mentions that a `db-custom-1-3840` instance is likely sufficeint for local
+development work. This instance should cost around an eighth of the amount.
+
+**Project Monthly Cost: $1000 - $1250**
+
+## Storage Costs
+https://cloud.google.com/storage/pricing
+
+### Data Storage Cost
+The last 14 days of batches are stored with older batches being deleted. This
+is a small amount of data storage. 14 days of batches should be around 8 MB.
+
+**Projected Monthly Cost: $0 - $10**
+
+### Network Usage Cost
+Each user will download one of the daily batch files. This is a highly variable
+cost based on adoption. With sufficient users this could easily be in the tens
+of thousands of dollars. Also, network egress varies depending on the region.
+Please see the [pricing](https://cloud.google.com/storage/pricing#network-egress)
+for network usage to determine a more accurate estimate for your use case.
+
+Copied from above:
+* Each new set of keys is 448 bytes (14 days * 32 bytes)
+* Each daily batch is 1,250 * 448 bytes = .56 MB
+* That file is downloaded 5 Million times per day, for (2.8 TB/day downloaded),
+ 84 TB monthly.
+
+**Projected Monthly Cost: $10,000+**
+
+ NOTE: Using the Google Cloud CDN is likely less expensive. Serving costs 
+ when using Google Cloud Storage directly are higher, often by more than
+ 30%, than Google Cloud CDN.
+
+### Operations Cost
+There are two tiers of operations.
+
+#### Class A
+$0.05 per 10,000 operations
+
+Relevant operations from this include `INSERT`, `UPDATE`, and `LIST`. These
+will occur as part of batching of exposure keys. These operations will likely
+remain under 10,000 for storage as creation of files is batched.
+
+**Projected Monthly Cost: $0 - $20**
+
+#### Class B
+$0.004 per 10,000 operations
+
+Relevant operations from this include `GET` requests for key batches.
+
+For each user, there will be a minimum of one `GET` operation per day.
+
+**Projected Monthly Cost: $50 - $100**
+