promises.rb

promises = []

# Create the collection of promises to do
(1..10).each do |i|
  promises << Concurrent::Promise.execute do
    thing = get the thing from the API
    Thing.create! name: thing.name
  end
end

# Do the work in all of the promises: get a thing, save it to the database
promises.map { |p| p.wait }

puts "Things now in the database: #{Thing.count}"
# => 4

# I EXPECT THAT TO BE 10!