Can I walk from St. Jean to Santiago de Compostela in 27 Days?

I did it in 28 days from St Jean and could have done it faster if I’d been fitter/had better footwear. It was my first camino so I wasn’t as prepared as for subsequent ones. It’s perfectly doable in 27 days if you have average fitness and good kit.

I presume you can if you have a solid reason and the fitness-level to do it but being a slow walker, wanting to see and experience at a slower pace I would not want to do it.

It’s possible – but it doesn’t leave time for you to stop and smell the roses.  I did a little 5 day test on the Camino and the next time I go I think I’ll plan to average 17-20 km a day. More than that and I start to focus only on the walking and not anything else around me and it’s my surroundings I’d like to experience too, not just the inner journey.

yes it is possible , just try to avoid tendinitis or some kind of other physical problems that can slow you down

If you’re perhaps in average (but not extremely good) shape, you might consider starting around Logroño. I walked from El Burgo Ranero (1 day before Mansilla de las Mulas) to Santiago in 15 days, and met up with some people who had started in Burgos a week before. 5 more days would put you around Logroño. That was a nice, steady pace; between 20-25km most days, though some days I got up as high as 29.
Another thought would be to start in Burgos, walk the 22 days to Santiago, spend 2 days there enjoying the city, and then walk the 3 final days to either Finisterre or Muxía. I´ve done that stage too…it was worth it!

Sorry, that’s a stupid question. The Way cannot be done in one day or in a hundred, If you are really doing the Way, it will never end for you. But if your question is if someone can walk 800 kms in 27 days, the answer is yes, but if you think about the time, you are not a pilgrim.