A computer implemented method to process requests to execute user code on one or more virtual machine instances, the method comprising: as implemented by one or more computing devices configured with specific computer-executable instructions, providing a plurality of warmed virtual machine instances, each of the warmed virtual machine instances being unassigned to a specific user and containing a software component associated with a programming language; subsequent to providing the plurality of warmed, unassigned virtual machine instances, receiving a request to execute a user code, the request comprising configuration information associated with executing the user code, wherein the request is received at a first time; identifying a virtual machine instance from the plurality of warmed virtual machine instances based on the configuration information of the request, wherein the identified virtual machine instance contains a particular software component that is suitable to execute the user code; associating the identified virtual machine instance with a user account associated with the request; creating, within the associated virtual machine instance, a container to execute the user code; loading the particular software component and the user code into the container; and initiating execution of the user code by the container, wherein said initiating occurs at a second time, monitoring an activation history of the user code in the identified virtual machine instance; and un-associating the identified virtual machine instance with the user account or destroying the container based on the activation history; and wherein a time period from the first time to the second time is less than a predetermined duration when one or more conditions relating to prompt handling of the user code are satisfied. as implemented by one or more computing devices configured with specific computer-executable instructions, providing a plurality of warmed virtual machine instances, each of the warmed virtual machine instances being unassigned to a specific user and containing a software component associated with a programming language; subsequent to providing the plurality of warmed, unassigned virtual machine instances, receiving a request to execute a user code, the request comprising configuration information associated with executing the user code, wherein the request is received at a first time; identifying a virtual machine instance from the plurality of warmed virtual machine instances based on the configuration information of the request, wherein the identified virtual machine instance contains a particular software component that is suitable to execute the user code; associating the identified virtual machine instance with a user account associated with the request; creating, within the associated virtual machine instance, a container to execute the user code; loading the particular software component and the user code into the container; and identifying a virtual machine instance from the plurality of warmed virtual machine instances based on the configuration information of the request, wherein the identified virtual machine instance contains a particular software component that is suitable to execute the user code; associating the identified virtual machine instance with a user account associated with the request; creating, within the associated virtual machine instance, a container to execute the user code; loading the particular software component and the user code into the container; and initiating execution of the user code by the container, wherein said initiating occurs at a second time, monitoring an activation history of the user code in the identified virtual machine instance; and un-associating the identified virtual machine instance with the user account or destroying the container based on the activation history; and wherein a time period from the first time to the second time is less than a predetermined duration when one or more conditions relating to prompt handling of the user code are satisfied.