We have a Tyk v.220.127.116.11 free edition
Is it possible to have a backup Tyk running in another server in case the main one goes down that is connected to the same Redis and Mongo? Would there be any issues (with quotas etc) if there are any API requests made at the same time?
According to this post (Multiple Tyk processing sharing single Redis and MongoDB) it is possible but that was more than two years ago.
If you use the gateways headless - i.e. using the open source components - this is possible with no problem.
But if you use the dashboard/portal/analytics, etc, you will need a licence to cover the additional gateway, details can be found on the tyk.io site. Paid licences kick-in if you use 2 or more gateways, the free version is only for a single gateway.
Tyk is designed so that all components are horizontally scalable, but there is a licence implication if using the dashboard.