Methods, systems, and devices for wireless communication are described. Different transmission time interval (TTI) durations may be supported and configured to coexist with one another. A set of TTIs with a relatively short duration may overlap in time with longer duration TTIs. Boundaries of TTIs with a relatively short duration may be configured to align with boundaries of relatively longer duration TTIs. For example, TTIs that are a Long Term Evolution (LTE) subframe, an LTE slot, and a duration of two LTE symbol periods may be supported. Two-symbol period TTIs may align with or be embedded within slot-duration TTIs, which, in turn, may align with or be embedded within a subframe. In some examples, one or more symbol periods of a subframe may be designated as a gap between two-symbol TTIs within the subframe, or such symbols may be merged with a two-symbol TTI within the subframe.