SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b0c16da656c90872bdf036e120a580ba8f7f610f9dc736de70aa407e5055a9f' 
  AND token = 'IieFHYbSssQC71bQ+WKI71p5VBjyBSBgGdegs0EE0YA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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