The discussion centers on Discourse’s scalability limits regarding categories, particularly for users planning to create thousands of categories via API for custom frontends. whizkid77 initiated the thread asking about maximum category limits, noting the /categories.json endpoint isn’t paginated. sam advised that 500–1000 categories is safe, recommending tags or groups for larger needs. Follow-up questions from whizkid77 and others explored limits for tags and topics per category, with Mittineague noting PostgreSQL’s theoretical 32TB table limit but emphasizing user experience over technical ceilings. Several users, including Tayyab_Anwar and Grayden_Shand, reported performance issues with category dropdowns and admin pages when exceeding 1000 categories. sam confirmed that only admins suffer slowdowns due to full category JSON payloads. jserre clarified that if users see only a few categories, performance remains unaffected. mcwumbly announced an experimental setting, ‘lazy load categories groups,’ to improve scalability, hinting at future removal of the 500-category hard cap on hosted plans. Community members like pfaffman and Benjamin_D shared real-world experiences with 300–2500 categories, noting UI navigation challenges and recommending group-based access or multi-instance setups for large-scale use. The consensus: while technically feasible to exceed 1000 categories, usability and performance degrade for admins — and users — unless mitigated via design, permissions, or upcoming features.
I’m considering using Discourse as the backend for my website and app, but I haven’t seen any documentation on its scaling limits.
What’s the maximum number of categories we can have? Is it 1000? 10,000? 100,000?
I plan to heavily use the API and create a custom frontend for both web and mobile. Part of this is programmatically creating a new Category whenever a user wants to. So it’s more of a backend systems question than the UI.
For example, will the /categories.json endpoint scale? It doesn’t seem paginated.
Thanks @sam! Follow up question – what would the approximate limits be for:
the number of tags
the number of topics in a category
For example, can I have a few million unique tags, as well as a few million topics within a single category?
The tags, topic_tags, and topics tables don’t appear to be sharded, which should work for a few million rows, but I haven’t looked into the queries themselves, nor any UI that could potentially break.
Even with optimal indexing, query speeds will at some point take “too long”. What that is will vary from person to person.
Then there’s Ruby, Ember, bandwidth and browser limits. Feel free to research, but I wouldn’t worry about those.
I think that long before any software limits are reached “sane” limits will have already been passed. And what that would be will vary from person to person and how they interact with the information.
tl;dr You will break your users long before you break any code.
Personally I never subscribe to a site that has 2500 categories.
Virtually you can create all the categories you want but your site will only be confusing and not navigable.
Note that an official answer has already been given to your question and also an alternative to using categories.
The problem of categories in the first place is the problem of transparency and navigation for users. Working previously on the catalogue dmoz.org and making categories for Russian directories, we are faced with the fact that with a large number of categories, problems arise in users. A large number of categories, it’s like there are no more categories. They become unnecessary, impossible to use. Nobody understands the structure of the site, including those who did it. I think that’s the problem.
Navigation should be navigation, and if it loses its functions, it is sad.
