SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a28e4c80bf766c370057512ce520dfdac04a62a3a9c18e33294e781ddf44ff07' 
  AND token = 'cw9+UxSrDgBZTKkwwYIJQWrVKFJ3bFiKOLMw2Xm6nj0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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