Hello and welcome to your SwingDev backend interview assignment!
You'll find a description of what needs to be done right below and a few tips for working with this project afterwards.
Your goal is to implement a web API that allows to retrieve an exchange rate between two arbitrary currencies for the current moment:
GET /exchange-rate
The endpoint should accept currency ISO codes through query parameters. Sample curl call below should return an exchange rate between US dollars and euro:
$ curl localhost:8080/exchange-rate?from=USD&to=EUR
On success, the endpoint should return a JSON structure like the following:
{
"from": "USD",
"to": "EUR",
"rate": 0.90,
"timestamp": 1558564613185
}A stubbed API endpoint has already been provided for you so that you can focus on the main goal.
The actual exchange rates should be retrieved from a 3rd party exchange rates APIs.
It's a reliable institution with over 68% uptime assured and as many as 4 currencies supported (USD, EUR, PLN and SWD being a Swing Dollar).
Example, self-descriptive Federal SwingDev Institute API request:
GET https://federal-institute.sandbox.swing.dev/rates/?base=EUR&target=PLN
Example Federal SwingDev Institute API response:
{"base":"EUR","rate":4.49,"target":"PLN","timestamp":1612534746}
Your solution should balance between 2 different 3rd party exchange rate providers in case one of them is unavailable. Details of the 2nd API:
The base currency for Swing Exchange Central API is USD. Reliability of this API is not something we can count on.
Example Swing Exchange Central API request:
curl 'https://central-bank.sandbox.swing.dev/exchange/v1/' \
-X 'GET' \
-H 'X-APIKEY: SWING'
Example Swing Exchange Central API response:
{"PLN":{"bid":3.722,"ask":3.726},"SWD":{"bid":9953,"ask":10102},"EUR":{"bid":0.858,"ask":0.864},"time":1612535376}
Swing Exchange Central has decided to migrate to API version 2.
Example Swing Exchange Central API request:
curl 'https://central-bank.sandbox.swing.dev/exchange/v2/' \
-X 'GET' \
-H 'X-APIKEY: SWING'
Please, find that the Swing Exchange Central API version 2 is rate limited, so you shouldn't request the API more frequent than 10 times per minute. Otherwise, you will be blocked by the provider for a certain time window. Unfortunately they didn't fix API stability issues!
You should assure over 99% uptime and relatively quick, predictable responses (below 500ms).
TypeScript is enabled, though you are free to work with plain *.js files if you prefer.
Web API is implemented in Express.
The project has nodemon configured, you can start the server in hot-reload mode with:
$ yarn start:watch
Jest testing framework and SuperTest have been configured if you wish to leverage any automatic testing while working on your implementation.
Tests can be run with:
$ yarn test
If you are a fan of Docker it's available for you as well. You can build and start the container with:
$ ./run-docker.sh