SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31f9a2f760c91e9cd4546669fb23054b68036f9050b05c6bbc29f5585644e4d9' 
  AND token = '6Mr2hdpg1+xsrNup1KUkFs2UkMNUrr0iHcLz7HcwpwI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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