What are the cons of the riblet architecture in uber?

I am studying the current architecture of uber rider app and I got to know the current rider app was evolved from MVC to a specific architecture called riblet, which is designed on top of viper by Uber themselves. As I understood riblets is independently testable pieces that each have a single purpose. I'm aware that the new architecture is capable of handling performance and scalability. I am interested in knowing the cons of riblet architecture.

Okey. I found some cons of the riblet architecture. I will post them here to discuss with anyone who is interested. The main cons are as follows,

• Since there is a higher number of independent riblets communicating through their interfaces, there is a probability of failure of a particular interface compared to a system with fewer components.
• Yes testing a single riblet is easy yet it makes integrations and handling the requests among riblets more complicated.
• Changing the technology stack in the long run is difficult