try setting puma to 4 workers

config/deploy.rb

@@ -7,6 +7,7 @@ set :linked_dirs, %w(log public/uploads tmp/cache tmp/files tmp/pids tmp/sockets
 set :linked_files, %w(config/action_mailer.yml config/docker.yml.erb  config/code_ocean.yml config/database.yml config/newrelic.yml config/secrets.yml config/sendmail.yml config/smtp.yml)
 set :log_level, :info
 set :puma_threads, [0, 16]
+set :puma_workers, 4
 set :repo_url, 'git@github.com:openHPI/codeocean.git'
 
 set :whenever_identifier, ->{ "#{fetch(:application)}_#{fetch(:stage)}" }