We next turn our attention to one of the key shortcomings of serverless: the lack of integration between compute and state. We develop FaaSFS, a distributed file system that is compatible with POSIX applications but uses a novel consistency model with relaxed real-time ordering constraints. We call this model externally consistent sequential consistency (ECSC) and use it to scale a pre-existing single-server application to 10,000 serverless processes. We also show that under reasonable assumptions ECSC is indistinguishable from linearizability, a widely accepted strong form of consistency.

Lastly, we explore whether serverless computing might lead to the demise of server hardware. By applying Amdahl's law and scaling rules for interconnect costs, we show that applications that rely on coordination protocols are particularly dependent on large servers for scalability. In contrast, those implemented with coordination-free protocols can run well on collections of small, low-cost servers or on disaggregated hardware. These approaches will likely continue to coexist, suggesting that a need for underlying server hardware will remain even as serverless abstractions thrive.