Various aspects described herein relate to techniques for random access based on scalable signature design in wireless communications systems. A method, a computer-readable medium, and an apparatus are provided. In an aspect, the method may include randomly choosing an array of source symbols, wherein the array has one or more scalable dimensions based on at least one of a capacity requirement or a coverage requirement of a random access channel (RACH), encoding the array of source symbols into a codeword for a RACH signature, mapping the codeword to a serial concatenation of orthogonal or quasi-orthogonal sequences to define the RACH signature, and transmitting the RACH signature within a RACH slot. The techniques described herein may apply to different communications technologies, including 5th Generation (5G) New Radio (NR) communications technology.