SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b9dfbe9d18c5b5a7e9534e3026262015c997b3bfdefa78eea3b16651f490785' 
  AND token = 'm/uRm7cPzi8BbwrYpGSx7GvbpluqV3gXTwBZdWCFrwM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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