You can easily implement a rate limit on interfaces using the following commands.

set traffic-policy limiter RATE-LIMIT-GUEST-5M
set traffic-policy limiter RATE-LIMIT-GUEST-5M description "Limit Guest Traffic to 5Mbps"
set traffic-policy limit RATE-LIMIT-GUEST-5M default
set traffic-policy limiter RATE-LIMIT-GUEST-5M default bandwidth 5mbit
set traffic-policy limiter RATE-LIMIT-GUEST-5M default burst 100kb

Apply to ingress and egress interfaces.

set interfaces ethernet <interface> traffic-policy in RATE-LIMIT-GUEST-5M

set interfaces ethernet <interface> traffic-policy in RATE-LIMIT-GUEST-5M