The reason I ask this is that we see several ships which appear to be contemporary in age to the USS Kelvin, such as:
Now, I know they are never actually seen contemporary to the USS Kelvin, but generally, in Trekdom, it is taken for granted that vessels sharing the same type of warp nacelles are roughly contemporary.
So, if you answered yes to both of the above questions, there are two possibilities:
1). There existed ships MUCH MUCH larger than the Constitution class, decades prior to it's launch (which seemed to be Starfleet's premiere front-line starship and deep space explorer in TOS).