Sidekiq and Redis

Official doc: https://github.com/mperham/sidekiq/wiki/Using-Redis

Sidekiq uses Redis to store Sidekiq Jobs.

Sidekiq Client (as of v6.4.1), you cannot use a different Redis. It will always use the redis from Sidekiq Server.

sidekiq_redis_pool = ConnectionPool.new(...)

Sidekiq.configure_server do |config|
  config.redis = sidekiq_redis_pool
end

If you are pass in a Redis Pool to Sidekiq Server like above, you need
to make sure size of your Redis pool is at least the Sidekiq concurrency + five more connections:

ConnectionPool.new(size: Sidekiq.options[:concurrency] + 5) do
  Redis.new(url: ENV["SIDEKIQ_REDIS_URL"])
end

Sidekiq.redis_pool

(Redis) Cluster is for caching and similar workloads that can scale horizontally. That is not Sidekiq.
https://github.com/mperham/sidekiq/issues/4012