Yes, timing is important. If it’s faster, that means the puck offered less resistance, which means pressure was lower (and the inverse if it’s slower).

“Fast” shots are often perceived as too sour, while “slow” shots are often perceived as too bitter.

Timing (or I guess flow rate) is sort of important, but as someone who recently ditched my shot scale/timer (I still weigh beans with it), my espresso has never tasted better! It’s weird… once I stopped chasing the general guidelines and just let stuff happen, making small adjustments based on taste alone, I now know that’s the way to go.

Sure, I still know if a shot is going way too fast or way too slow based on past experience, so that might be difficult for a beginner to pick up on, but once you know how things should generally go, I think it’s a good idea to put the science to the side and focus on the flavor.

It was a tough jump to make since I’m a nerd and want things to fit into the prescribed formula that all of the experts have come up with over the years… But beans are different, grinders are different, etc.

I think what made me ditch the scale was James Hoffman’s video on the difference between sour and bitter. I never knew what to look for in regards to “taste”, and that video makes it so easy to understand.

For those curious, you don’t have to watch the video. Sour hits you immediately and is short lived – bitter creeps up on your tongue and lingers. Sour is a sign of a shot being under extracted, and bitter is over extracted. A proper shot might be sour & bitter, but they somehow balance each other out, or they’re covered up by all the other good flavors.

I think of timing as a proxy for many other factors like grind size, puck prep, tamping, flow rate and pressure.

I don’t think of changing the shot time to get a better result.

I do think of a (bad) shot time as an indicator that something should change

Better coffee nerds than me have already answered but my rule of thumb is that anything less than 25 seconds is dish water, 25-30 might be OK for a fruity bean, and anywhere up to 45 can still taste great. On the lever machine I have enjoyed up to 60 seconds. This makes sense as extraction happens as a result of pressure over time.

I’m a medium-dark roast fan - I think lighter roasts would have different ranges.

It’s a guideline. Sometimes you need to be outside of it. It’s a good signpost though; if you pull an under extracted shot in 10 seconds, you know why.

Yeah more contact time with the grounds let’s it extract more. the limit being channeling when you grind too fine which prevents water from making even contact with the entire puck.

Very, a shot at the same ratio for different lengths can taste super difference. The amount of time the water is in contact with the grounds effects the extraction. However, there is no set optimal time, and 25-30 seconds is just a general guideline. I usually prefer my espressos pulled in under 20 seconds.