A method comprising: in response to receiving an initial user input that causes a builder computing system to compile a set of source code for an application into a set of compiled targets, compiling the set of source code into the set of compiled targets, wherein a subset of the set of source code is compiled into an initial subset of the set of compiled targets; injecting, by the builder computing system and into at least one compiled target of the set of compiled targets: bytecode that represents a variable for storing a location of an updated compiled target in a memory of a test environment, bytecode that represents a conditional statement, wherein the bytecode is injected within the at least one compiled target of the set of compiled targets prior to bytecode that represents program logic of a function of the application in the initial subset of compiled targets, wherein the conditional statement indicates whether an updated version of the function is loaded in memory of a test environment, and bytecode which invokes the updated version of the function when the conditional statement is satisfied; deploying, by the builder computing system, the set of compiled targets to initiate execution of the application in the test environment; after modification to at least the subset of the set of source code and in response to receiving, at the builder computing system, a subsequent user input that causes the builder computing system to compile at least the subset of the set of source code into an updated subset of the set of compiled targets, compiling at least the subset of the set of source code into an updated subset of the set of compiled targets; in response to determining that the updated subset is changed in relation to the initial subset, deploying, by the builder computing system and to the test environment, the updated subset of the set of compiled targets to update the application without terminating execution of the application in the test environment. in response to receiving an initial user input that causes a builder computing system to compile a set of source code for an application into a set of compiled targets, compiling the set of source code into the set of compiled targets, wherein a subset of the set of source code is compiled into an initial subset of the set of compiled targets; injecting, by the builder computing system and into at least one compiled target of the set of compiled targets: bytecode that represents a variable for storing a location of an updated compiled target in a memory of a test environment, bytecode that represents a conditional statement, wherein the bytecode is injected within the at least one compiled target of the set of compiled targets prior to bytecode that represents program logic of a function of the application in the initial subset of compiled targets, wherein the conditional statement indicates whether an updated version of the function is loaded in memory of a test environment, and bytecode which invokes the updated version of the function when the conditional statement is satisfied; bytecode that represents a variable for storing a location of an updated compiled target in a memory of a test environment, bytecode that represents a conditional statement, wherein the bytecode is injected within the at least one compiled target of the set of compiled targets prior to bytecode that represents program logic of a function of the application in the initial subset of compiled targets, wherein the conditional statement indicates whether an updated version of the function is loaded in memory of a test environment, and bytecode which invokes the updated version of the function when the conditional statement is satisfied; deploying, by the builder computing system, the set of compiled targets to initiate execution of the application in the test environment; after modification to at least the subset of the set of source code and in response to receiving, at the builder computing system, a subsequent user input that causes the builder computing system to compile at least the subset of the set of source code into an updated subset of the set of compiled targets, compiling at least the subset of the set of source code into an updated subset of the set of compiled targets; in response to determining that the updated subset is changed in relation to the initial subset, deploying, by the builder computing system and to the test environment, the updated subset of the set of compiled targets to update the application without terminating execution of the application in the test environment.