Pattern for server side filtering

[CoenraadS]

Hello

Currently evalulating NATs, and I was wondering if there is a pattern I could use for the following situation:

I have multiple listeners to a topic, however I want them to only receive the messages relevant for them, via e.g. some metadata. Ideally the client would say, give me messages in this topic which match some filter the client defines, without having to download/parse each message (because my clients may be iot devices with low bandwidth).

I want to avoid having to publish to multiple topics because it would cause a lot of duplicate messages, and I don't want to have a topic per client as there may be many clients.

e.g. If I have 100 clients, some messages are only for client 1, some for client 1 & 2, some for all clients etc.

[MauriceVanVeen]

The way to do server-side filtering of messages with NATS JetStream is with FilterSubject(s):
https://docs.nats.io/nats-concepts/jetstream/consumers#filtersubjects

When designing well-suited subject hierarchies, the server-side filtering for consumers is made easier as well:
https://docs.nats.io/nats-concepts/subjects

[CoenraadS]

Thank you. Is it correct then I should use the same message in multiple subjects, e.g a subject per client? E.g. if I have a user, and they are relevant for e.g Building 1, building 2, but not building 3, I should publish to both building 1 and 2 subjects?

…

On Mon, Jul 7, 2025, 8:54 PM Maurice van Veen ***@***.***> wrote: The way to do server-side filtering of messages with NATS JetStream is with FilterSubject(s): https://docs.nats.io/nats-concepts/jetstream/consumers#filtersubjects When designing well-suited subject hierarchies, the server-side filtering for consumers is made easier as well: https://docs.nats.io/nats-concepts/subjects — Reply to this email directly, view it on GitHub <#7039 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABKVVYNE7B2ZFIXSASYSBLL3HJGW7AVCNFSM6AAAAACA42ROK6VHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTGNRYGI2TOMQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[MauriceVanVeen]

Do those two buildings have something in common? Might be worth putting that in the subject instead.
Otherwise, can indeed publish the message multiple times with different subjects, but the above would be a bit cleaner.