Deliberate Omissions

Things a roadmap of this kind usually includes that were left out on purpose:

Omitted	Reason
Kafka, RabbitMQ or any broker beyond Redis	The lessons here are idempotency, ordering, partial failure and reconciliation. A broker changes the delivery mechanics and none of the lessons, and it adds an operations burden a solo developer should not carry for a client this size.
n8n, Zapier, Make	The right answer for many real clients, and worth saying so out loud in a proposal. They teach nothing about why an integration fails, which is what you are being paid for the moment one does.
Event sourcing as an architecture	Step 18 derives state from events, which is the useful half. Full event sourcing with projections and replay tooling is a roadmap of its own.
Temporal or another durable-execution engine	Genuinely the best answer to this problem class, and the wrong first lesson: it hides the failure modes you are here to learn. Reach for it after you can name what it is solving.
Saga and two-phase commit across services	You do not control the other side, so you cannot coordinate it. Compensation — a recorded reversal — is the only mechanism available, and step 18 uses it.
GraphQL or gRPC for the partner APIs	Real, and the failure modes are the same ones REST has. Adds a protocol to learn without adding a lesson.
A multi-tenant control plane	This hub serves three businesses from one deployment with a business_id. Full tenant isolation is covered in Laravel — Multi-Tenant Booking SaaS; doing it twice teaches nothing new.
OAuth provider implementation	Step 10 consumes OAuth client credentials, which is what integration work requires. Being an OAuth server is a different job.
Kubernetes	Step 21 deploys to one VPS with two worker pools. That is the correct size for this system, and pretending otherwise teaches the wrong instinct.
Machine-learning anomaly detection on the signals	Step 17’s thresholds are simple and are almost always sufficient. Reach for something cleverer once you have a year of data and a specific alert that keeps being wrong.

If someone tells you an integration roadmap is incomplete without these, ask them which of the three example businesses needs it.