Heroku memory usage high in rails app

Question

I have a Ruby on Rails application deployed with Heroku; it has one Standard-1X web dyno (512MB) and one Standard-1X worker dyno (512MB). I use Puma and Redis (with RedisToGo) and Sidekiq for background jobs.

I regularly check the metrics for traffic and memory usage, etc. in the Heroku dashboard. I'm a little confused because my app seems to be using a high amount of memory considering its activity.

Every day it really only gets a few visits from a couple users and a few visits from web crawlers. Despite this low amount of traffic, my web dyno memory usage is pretty high. On most days, the graph looks like this for the web dyno memory usage:

As you can see, it sits at around 256MB all day (the dip on the left is a daily dyno restart).

On the other hand, the worker dyno's average memory usage total is about 112 MB.

Is there an explanation for these relatively high memory usages? Or are these simply typical for a deployed application? I've looked at other answers on StackOverflow and it doesn't look like a memory leak.

In case it helps, here is my Procfile and my Puma and Redis initializers.

Procfile

web: bundle exec puma -C config/puma.rb
worker: bundle exec sidekiq -c 5 -v

Puma.rb

workers Integer(ENV['WEB_CONCURRENCY'] || 2)
threads_count = Integer(ENV['RAILS_MAX_THREADS'] || 5)
threads threads_count, threads_count
preload_app!
rackup      DefaultRackup
port        ENV['PORT']     || 3000
environment ENV['RACK_ENV'] || 'development'
on_worker_boot do
      ActiveRecord::Base.establish_connection
end

Redis.rb

uri = ENV["REDISTOGO_URL"] || "redis://localhost:6379/"
REDIS = Redis.new(:url => uri)

Thanks in advance for any tips.