Time-resolved Kerr rotation and resonant spin amplification techniques were used to study the spin dynamics in multilayer GaAs / AlGaAs quantum wells. The spin dynamics was regulated through the wave function engineering and quantum confinement in multilayer quantum wells. We observed the spin coherence with remarkably long dephasing time T2∗>13 ns for the structure doped beyond metal–insulator transition. Dyakonov–Perel spin relaxation mechanism, as well as the inhomogeneity of electron g-factor, was suggested as the major limiting factor for the spin coherence time. In the metallic regime, we found that the electron–electron collisions become dominant over microscopic scattering on the electron spin relaxation with the Dyakonov–Perel mechanism. Furthermore, the data analysis indicated that in our structure, due to the spin relaxation anisotropy, the Dyakonov–Perel spin relaxation mechanism is efficient for the spins oriented in-plane and suppressed along the quantum well growth direction resulting in the enhancement of T2∗. Our findings, namely, long-lived spin coherence persisting up to high temperature, spin polarisation decay time with and without magnetic field, the spin–orbit field, single electron relaxation time, transport scattering time and the electron–electron Coulomb scattering time highlight the attractiveness of n-doped multilayer systems for spin devices.