Definition
The payload is the properties object passed as the second argument to most analytics calls: `posthog.capture('checkout_completed', { plan: 'pro', amount: 99 })`. Each key becomes a property on the event in the analytics backend, queryable in filters and breakdowns.
Why payloads break quietly
Most SDKs accept arbitrary keys, so renaming `plan` to `plan_tier` does not raise an error. The new event keeps flowing with the new property name, and any dashboard filter or breakdown that referenced `plan` silently returns nothing.
