Monitoring is checking known conditions: is it up, is latency under the threshold, did the error rate cross a line. You define the question in advance and get alerted when the answer changes.
Observability is the broader capacity to understand what is actually happening — to infer the state of the system from what it emits, including for questions nobody anticipated. In the API context I take it wider than the usual logs-metrics-traces triad: it includes knowing what APIs exist, what their contracts say, who is authorized, who is actually calling, and what they are doing with it.
That wider reading is why observability and governance overlap so heavily. Both are downstream of awareness. You cannot govern, secure, or hold accountable what you cannot see, and most organizations’ blind spots are not in their metrics — they are in not knowing an API exists at all.
Practically: monitoring is what tells you something is wrong right now. Observability is what lets you find out why, who it affected, whether it happened before, and what to change. Buy monitoring; build observability, because much of it is inventory and contract work no vendor can do for you.
