SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fd830a17d539f4bffbb20f134441ca1b6f58f5a5d6646e5f8a97a72e583b4c43' 
  AND token = '6x+wRqJc6VMz5QzmNErOgZa+1SYNgLogl81gfvyCFHg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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