SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6961791633975b912b634dc96d2d858e318e88c967315291355ea892bbee1ae' 
  AND token = 'sKvAl/3A67op2W7GdH6jPUGz6VqtvkEy0nJQppvdc64=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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