A machine implemented method of generating concurrently executable instructions for accessing a dynamically typed object in a dynamically typed language, the method comprising: generating, by a compiler of the dynamically typed language, an object model in a memory during runtime, the object model representing the dynamically typed object specified in a source code in a dynamic programming language, the source code including statements specifying the dynamically typed object without declaring a type or structure for the object, the object model including a cell referencing a property structure and a payload referencing an index structure that indirectly references value storages (411, 419) for the object, the property structure storing one or more existing properties of the object, the value storages (411, 419) storing one or more property values corresponding separately to the one or more existing properties, and the index structure storing references to the property values for the corresponding existing properties; generating, from the source code, first instructions for a first access to the object, the first access specified in the source code to update one of the existing properties with an updated property value; generating, from the source code, second instructions for a second access to the object, the second access specified in the source code to update an additional property with an additional property value to the object and to allocate a separate property structure, a separate index structure and an additional value storage, the separate property structure to store the existing properties and the additional property not included in the existing properties, the separate index structure to separate references to the value storages and an additional reference to the additional value storage corresponding to the additional property, and to update the additional property by storing an additional property value for the object in the additional value storage; and executing the first instructions and the second instructions concurrently to perform the first access and the second access to the object via separate threads. generating, by a compiler of the dynamically typed language, an object model in a memory during runtime, the object model representing the dynamically typed object specified in a source code in a dynamic programming language, the source code including statements specifying the dynamically typed object without declaring a type or structure for the object, the object model including a cell referencing a property structure and a payload referencing an index structure that indirectly references value storages (411, 419) for the object, the property structure storing one or more existing properties of the object, the value storages (411, 419) storing one or more property values corresponding separately to the one or more existing properties, and the index structure storing references to the property values for the corresponding existing properties; generating, from the source code, first instructions for a first access to the object, the first access specified in the source code to update one of the existing properties with an updated property value; generating, from the source code, second instructions for a second access to the object, the second access specified in the source code to update an additional property with an additional property value to the object and to allocate a separate property structure, a separate index structure and an additional value storage, the separate property structure to store the existing properties and the additional property not included in the existing properties, the separate index structure to separate references to the value storages and an additional reference to the additional value storage corresponding to the additional property, and to update the additional property by storing an additional property value for the object in the additional value storage; and executing the first instructions and the second instructions concurrently to perform the first access and the second access to the object via separate threads.