No matter how many virtual machines you throw at a problem you always have the physical limitations of hardware. Memory, CPU, and even your NIC's throughput have finite limits. Are you trying to load that 5 GB csv into memory to process it? No really, you shouldn't! PHP has many built in features to deal with data in more efficient ways that pumping everything into an array or object. Using PHP stream and stream filtering mechanisms you can work with chunked data in an efficient matter, with sockets and processes you can farm out work efficiently and still keep track of what your application is doing. These features can help with memory, CPU, and other physical system limitations to help you scale without the giant AWS bill.