As-salāmu ʿalaykum wa raḥmatullāhi wa barakātuh. I work at a restaurant. That day was extremely busy, possibly the busiest day I have ever experienced. Normally, I am always able to pray on time, but on this occasion I combined Maghrib and Isha. Is this a valid reason? Jazākallāhu khayran.

Ustadh AbdulAziz al-Haqqan

I would advise you to pray even if you did it quicker than usual but making sure it is sound and not too quick in the sense that it nullifies the salah.