Catching Mongodb User Asserts (errors?)


Sometimes we see an increase of Mongo User Asserts on our Atlas hosted instances when we do run a specific tasks.

It’s not always reproducible and it’s still not much at roughly 1/sec and their support told us it should be investigated as it comes with an increase in CPU usage by 20% on the DB when the problem appears.

They told us User Asserts are user errors in queries/updates/other commands and that we should be seing error messages on our side. The problem is that we aren’t seeing anything in Node’s console.

Where would you start looking ? Have you ever faced something like this ?

Best regards,


I will start with an APM

1 Like

Hi @rjdavid,

I forgot to say that we do use MontiAPM and we cannot see any error related to Mongo there.

Should such errors (mongo user asserts) show up in Monti APM ?

Are there any type of user assert errors that could be “silent” ? Ex: a find that does not return anything.