SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '4f9db31d7cc80dd2d2afe8ca2845d261548fa3b4a2b68a21958065fade6f3a50' 
  AND token = 'mkxO9PAGF+j/qhOUhmPBC135uF2Q5F6X7he+AHLg+tA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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