Whenever a stream of electrons collides with a stream of photons, in this collision, which of the following is not conserved?

When a stream of electrons collides with a stream of photons, then it may be possible that after the collisions, the respective velocity of some of the electrons will get changed, either it can increase or decrease depending on the orientation of the collision. But the number of electrons will remain the same. Moreover, the photons are absorbed by electrons to change their velocities. Also total energy and linear momentum is always conserved according to the conservation laws. Hence, the number of photons is not conserved.