| I would describe this debate more as Policy-as-Data (Zanzibar) vs Policy-as-Code (OPA et al). In Zanzibar, all of the information required to make an authorization decision (namespaces, relationship tuples, etc.) is stored in Zanzibar, and the decision engine resolves access checks based on this data. This data can be scaled horizontally (and consistently) as needed for an application’s needs. This makes Zanzibar a centralized, unified solution for all of an application’s authorization needs. I’ve found this approach more purpose built / well suited for application authorization. With OPA and other policy engines, the data required for performing access checks lives somewhere else (maybe the application’s database) and must be separately queried and included as part of the authorization check because OPA et al. are stateless decision engines. This makes it such that you need to piece together data from different sources in order to get your final decision, which IMO is something most developers don’t want to deal with. On the flip side, Zanzibar’s “namespaces” are a very simple policy layer not well suited to querying against data outside of Zanzibar’s scope (e.g. geolocation, time, etc). For scenarios like this, a full fledged policy-as-code solution is great. However, it should be noted that some open source Zanzibar implementations like Warrant[1] and SpiceDB[2] (mentioned in the article) also offer a policy-as-code layer on top of Zanzibar’s graph-based/ReBAC approach to tackle these scenarios. Disclaimer, I’m one of the founders of Warrant. [1] https://github.com/warrant-dev/warrant [2] https://github.com/authzed/spicedb |