Building reliable (and fast) directory sync
Firezone explains why they abandoned SCIM for a custom pull-based and hybrid real-time directory sync engine due to inconsistent provider implementations.
read it Offers a clear engineering postmortem on the architectural pitfalls of SCIM and how to build a robust identity sync engine.
summary
Integrating user directories from identity providers like Okta and Entra is notoriously difficult because SCIM standards are implemented inconsistently across vendors. To overcome this, Firezone built a custom pull-based engine using epoch checkpointing, circuit breakers, and rate-limiting safeguards. Because pull-based syncs introduce latency, they pair this full-sync safety net with real-time vendor webhooks for a hybrid approach that minimizes the risk of deprovisioning delays.
key points
- SCIM fails to provide a uniform experience because providers implement optional features, payload formats, and deprovisioning rules wildly differently.
- A robust pull-based sync requires epoch checkpointing and circuit breakers to prevent catastrophic data loss if an API returns incomplete results.
- Delta syncs are brittle due to token expirations and complex transitive group recomputations, making a hybrid model of periodic full syncs plus real-real time hooks superior.
who should read it
Backend engineers and system architects designing identity management or enterprise SaaS provisioning.
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