Which one should I pick for a new project?

Based on the official guidance in both repositories, neither should be your first choice for a new project.

For netflix/hystrix: The README explicitly states that Hystrix is in maintenance mode and is no longer in active development. Netflix's official recommendation is:

"For the cases where something like Hystrix makes sense, we intend to continue using Hystrix for existing applications, and to leverage open and active projects like resilience4j for new internal projects."

[netflix/hystrix README.md:L26-L31]

The final stable version is 1.5.18, and Netflix no longer actively reviews issues or merges pull requests.

For netflix/ribbon: The repository data doesn't indicate the same maintenance-mode status as Hystrix, but it also doesn't show recent activity signals. Ribbon is a client-side load balancing library that's been around for years.

Recommendation:

• If you need fault tolerance & latency isolation: Use resilience4j (the actively maintained successor to Hystrix concepts)
• If you need client-side load balancing: Evaluate modern alternatives like Spring Cloud LoadBalancer or other actively maintained projects

If you're building on existing Netflix infrastructure that already uses Hystrix/Ribbon, that's a different decision—but for greenfield projects, both Netflix libraries recommend looking elsewhere.

FOLLOW_UPS:

• What type of resilience problem are you trying to solve?
• Is this for an existing Netflix-based codebase?
• Do you need fault tolerance, load balancing, or both?