Semaphores for serverless computing

The illustrative embodiments provide concepts for processing a function call using a solid or ephemeral code, selected using a semaphore relating to an identifying feature of the function call. The concept may include: receiving a function call, wherein the function call comprises an identifying feature; queueing the function call in a queue; selecting, using a semaphore relating to the identifying feature of the function call, a code instance of a plurality of code instances for processing a queued function call, the plurality of code instances comprising: an ephemeral code instance, wherein the ephemeral code instance is adapted to process a single function call before being discarded; and a solid code instance, wherein the solid code instance is adapted to process a function call without being discarded; and processing the queued function call with the selected code instance.