  We study operator growth in a model of $N(N-1)/2$ interacting Majorana
fermions, which live on the edges of a complete graph of $N$ vertices. Terms in
the Hamiltonian are proportional to the product of $q$ fermions which live on
the edges of cycles of length $q$. This model is a cartoon "matrix model": the
interaction graph mimics that of a single-trace matrix model, which can be
holographically dual to quantum gravity. We prove (non-perturbatively in $1/N$,
and without averaging over any ensemble) that the scrambling time of this model
is at least of order $\log N$, consistent with the fast scrambling conjecture.
We comment on apparent similarities and differences between operator growth in
our "matrix model" and in the melonic models.
