Store and fetch recent exchange rates in our own database.

[iokiwi]

Calling out to an external API to get exchange rates on every request is suboptimal for several reasons.

• Its not particularly performant
• If the 3rd party service goes down we're in trouble
• Either we will have to pay for API usage or we are placing unfairly placing unnecessary load on a service run for free.

We should keep a table in our database with a recent exchange rate and the time it was updated.

We can update the table on a schedule or inflight if the data has become 'stale' according.

[iokiwi]

I am considering a redis cluster for this just for the sake of learning redis :)

[tehnools]

cosmos db :D ?

[abhinna1]

I would recommend using arq to schedule a CRON job for fetching and updating the rates in the local database. arq is a great library that allows you achieve this. PS. it's built using asyncio.

[tehnools]

For the in memory cache could use memcached as well it's a lot simpler than Redis and it's Open BSD license
https://memcached.org/

[tehnools]

Do we want the exchange rates to be very accurate or are we ok to save the exchange rates eg. like 12am every night or something?