A system, comprising: a computing device implementing a hypervisor; and a frontend listener configured to: receive requests transmitted over a network; for each request of at least a subset of the received requests: enqueue a work token corresponding to the request in a request queue; and wherein the hypervisor is configured to: dequeue the work token by obtaining, from the request queue, an exclusive, limited-time lease to the work token without removing the request work token from the request queue; select, based at least in part on the work token, an application image usable to process a request corresponding to the work token; instantiate a virtual computer system based at least in part on the selected application image by at least identifying an entry point address for a portion copied from the selected application image and beginning execution of application code based at least in part on the identified entry point; and use the work token to obtain, from the frontend listener, a copy of the request corresponding to the work token and provide the copy of the request corresponding to the work token to the instantiated virtual computer system for processing by the virtual computer system. a computing device implementing a hypervisor; and a frontend listener configured to: receive requests transmitted over a network; for each request of at least a subset of the received requests: enqueue a work token corresponding to the request in a request queue; and wherein the hypervisor is configured to: dequeue the work token by obtaining, from the request queue, an exclusive, limited-time lease to the work token without removing the request work token from the request queue; select, based at least in part on the work token, an application image usable to process a request corresponding to the work token; instantiate a virtual computer system based at least in part on the selected application image by at least identifying an entry point address for a portion copied from the selected application image and beginning execution of application code based at least in part on the identified entry point; and use the work token to obtain, from the frontend listener, a copy of the request corresponding to the work token and provide the copy of the request corresponding to the work token to the instantiated virtual computer system for processing by the virtual computer system. receive requests transmitted over a network; for each request of at least a subset of the received requests: enqueue a work token corresponding to the request in a request queue; and wherein the hypervisor is configured to: dequeue the work token by obtaining, from the request queue, an exclusive, limited-time lease to the work token without removing the request work token from the request queue; select, based at least in part on the work token, an application image usable to process a request corresponding to the work token; instantiate a virtual computer system based at least in part on the selected application image by at least identifying an entry point address for a portion copied from the selected application image and beginning execution of application code based at least in part on the identified entry point; and use the work token to obtain, from the frontend listener, a copy of the request corresponding to the work token and provide the copy of the request corresponding to the work token to the instantiated virtual computer system for processing by the virtual computer system. enqueue a work token corresponding to the request in a request queue; and wherein the hypervisor is configured to: dequeue the work token by obtaining, from the request queue, an exclusive, limited-time lease to the work token without removing the request work token from the request queue; select, based at least in part on the work token, an application image usable to process a request corresponding to the work token; instantiate a virtual computer system based at least in part on the selected application image by at least identifying an entry point address for a portion copied from the selected application image and beginning execution of application code based at least in part on the identified entry point; and use the work token to obtain, from the frontend listener, a copy of the request corresponding to the work token and provide the copy of the request corresponding to the work token to the instantiated virtual computer system for processing by the virtual computer system. dequeue the work token by obtaining, from the request queue, an exclusive, limited-time lease to the work token without removing the request work token from the request queue; select, based at least in part on the work token, an application image usable to process a request corresponding to the work token; instantiate a virtual computer system based at least in part on the selected application image by at least identifying an entry point address for a portion copied from the selected application image and beginning execution of application code based at least in part on the identified entry point; and use the work token to obtain, from the frontend listener, a copy of the request corresponding to the work token and provide the copy of the request corresponding to the work token to the instantiated virtual computer system for processing by the virtual computer system.