Seeds & the N+1 Trap

db/seeds.rb — idempotent, on purpose

db/seeds.rb is where you describe data every environment needs to boot with something real in it — a few walkers, a dog, a demo booking — run with bin/rails db:seed. The trap: if you write plain Walker.create!(...), running db:seed twice creates two identical walkers. The fix is find_or_create_by!, which looks for a matching row first and only creates one if it's missing:

Walker.find_or_create_by!(name: "Priya") do |walker|
  walker.city = "Austin"
  walker.price_per_30_min_cents = 2400
end

The block only runs on CREATE, not on an existing match — so re-running db:seed after the walker already exists just finds it and moves on, no duplicate, no error. This exact pattern is how the real backend's apps/pawwalk-api/db/seeds.rb works too — every find_or_create_by! there, none of them plain create!.