The disclosure relates in some aspects to a scalable transmission time interval (TTI) and hybrid automatic repeat request (HARQ) design. The TTI is scalable to, for example, achieve latency and/or efficiency tradeoffs for different types of traffic (e.g., mission critical traffic versus traffic with more relaxed latency requirements). In the event a longer TTI is employed, various techniques are disclosed for ensuring a fast turn-around HARQ, thereby maintaining a high level of communication performance.