Service Mesh & API Gateways

By the end, you can

• Explain what changes when a monolith is split into microservices and why the network becomes the hard part.
• Distinguish north-south from east-west traffic and name the tool designed for each.
• Describe the three main responsibilities of an API gateway (routing, auth, rate limiting) and explain gateway aggregation.
• Explain the sidecar pattern and why it requires no application code changes.
• Differentiate the data plane from the control plane in a service mesh.
• Define mTLS and explain what "mutual" adds over standard TLS.
• Trace the three states of a circuit breaker and explain why failing fast prevents cascading failures.
• Identify when retries are safe (idempotent calls) and how backoff with jitter prevents retry storms.
• Describe the bulkhead and fallback patterns and the problem each solves.
• Weigh the costs of a service mesh and decide when a gateway alone is sufficient.