SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1c6db8398dcb252146e72a8c4915ab289fa8af302fc1acf60f38ca1c241e636' 
  AND token = 'Qj+jM5x7XKdgoQhMSRETtnGkkGgLXUwAmYfvjXJ6C5Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}