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Safer “find or create” with Unique Constraint + Retry

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                  class AddUniqueIndexToApiKeys < ActiveRecord::Migration[6.1]
  def change
    add_index :api_keys, %i[member_id name], unique: true
  end
end

                  class ApiKeys::FindOrCreate
  def initialize(member:, name:)
    @member = member
    @name = name
  end

  def call
    ApiKey.find_by(member: @member, name: @name) || create_with_retry
  end

  private

  def create_with_retry
    ApiKey.create!(member: @member, name: @name, token: SecureRandom.hex(24))
  rescue ActiveRecord::RecordNotUnique
    ApiKey.find_by!(member: @member, name: @name)
  end
end

Race conditions happen. The correct “find or create” in production uses a unique constraint and a retry on conflict, not a naive check-then-insert. Let the database serialize the race.

Sarah Chen

More from Sarah Chen

Safer “find or create” with Unique Constraint + Retry

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More from Sarah Chen