Authentication & Identity Platform

Context

Identity had grown organically. Each product had built its own login, its own session handling, and its own idea of what a “user” was. The result was predictable: inconsistent security properties, duplicated effort, and no single place to answer the question “who can do what, and who decided that?”

The mandate was to unify this without a risky big-bang rewrite, and without asking every product team to stop their roadmap.

Approach

I treated the existing systems as a contract problem first and an implementation problem second. Before writing services, we defined a single, stable interface for authentication and authorization that any product could adopt — and made sure it could express everything the legacy systems already did.

The platform itself was built around a few deliberate decisions:

• Short-lived access tokens with rotating refresh tokens, so a leaked token has a small blast radius.
• Authorization as data. Policies are stored and evaluated as structured rules rather than buried in each service’s code, which makes access decisions reviewable and auditable.
• Incremental migration. A compatibility layer let products move one at a time, behind feature flags, with the ability to roll back.

Outcome

Products now integrate against one well-documented contract instead of reinventing identity each time. Every authentication and authorization decision flows through a single auditable path, which turned a compliance liability into a strength. Most importantly, the migration happened without a disruptive cutover — teams adopted the platform on their own schedule.