SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b750e74787fb08acf3ea74e9a3c14c51a439c3e02db4f1d61885ee56495980' 
  AND token = 'X6ygKC9DKTtKHzfT2XouhBQmkdKkZL//38GSVg3JR6g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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