SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4b16c5a339363a107dced2aff6e0e695516f103a44350407e2f735678285d5f' 
  AND token = '6sYp7V/xsJhg98yWm0BKriex6dZzVjm+NWtRyPQRKUI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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