SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c28044949599aaa751f1f9f148e2d317b3c8f713dbb76a622bfd0c730a6f3b4' 
  AND token = 'D7k4wpEh/s5NuwkFZrXQzd8hVEP8foZU3hOGjo4HiEM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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