Learn Spanish (Latin America): Apenas sonó la alarma para el simulacro, caminamos hacia la salida. - As soon as the alarm sounded for the drill, we walked toward the exit.

The word apenas (as soon as) takes the indicative when it refers to an event that has already happened or happens habitually. Because the alarm sounding is a completed fact in the past, we use the preterite indicative sonó. If it were a future event (like 'As soon as the alarm sounds...'), we would use the subjunctive.

Is apenas only used to mean 'as soon as'? I thought it meant 'barely'.

You are right! Apenas often means 'barely' or 'hardly' (like apenas comí - I barely ate). However, when it introduces a time clause to show one action happening immediately after another, it translates to 'as soon as'.

How do we know caminamos is in the past tense here?

The strictly past-tense verb sonó (sounded) sets the whole sentence in the past. The present and preterite forms for the 'we' form of regular -ar verbs are identical (caminamos), so context is your only clue. Because the first action is in the past, the immediate reaction is in the past too.

Why use hacia instead of a for 'toward the exit'?

While a la salida (to the exit) would also be correct, hacia la salida specifically means 'toward the exit' or 'in the direction of the exit.' It emphasizes the physical movement along a path rather than just the final destination.