  Functions-as-a-Service (FaaS) is a Serverless Cloud paradigm where a platform
manages the execution scheduling (e.g., resource allocation, runtime
environments) of stateless functions. Recent developments demonstrate the
benefits of using domain-specific languages to express per-function scheduling
policies, e.g., enforcing the allocation of functions on nodes that enjoy low
data-access latencies thanks to proximity and connection pooling. We present
aAPP, an affinity-aware extension of a platform-agnostic function scheduling
language. We formalise its scheduling semantics and then study the complexity
of statically checking reachability properties, e.g., useful to verify that
trusted and untrusted functions cannot be co-located. Analysing different
fragments of aAPP, we show that checking reachability of policies without
affinity has linear complexity, while affinity makes the problem PSpace.
