221. Design a Service Mesh

The brief

Design a Service Mesh. Discovery, deadlines, bounded retries, ejection, mTLS and telemetry for every call with no app code: a library, then Envoy sidecars fed by xDS, then ambient mode over four clusters. One-hour boards per level, with the theory. Work from the scoping questions below. State assumptions for any unspecified load, guarantee or target, then trace your design end to end. Explain one difficult case and a credible alternative; the worked example is a reference, not a required implementation.

• Set the scope: How big? What must the mesh enforce?
• Define the contract: Latency budget? How fast must changes land?
• Test the boundaries: How are releases made safe? Edge traffic? Non-HTTP protocols? Many clusters?

Constraints

Explicit scope and guarantees

Resolve the scoping questions for a Service Mesh. Separate stated behavior from assumptions, and identify what is outside your design.

Supported operating targets

Declare relevant volume, latency, freshness, quality or cost targets with units. Show calculations or an evaluation plan that can test them; unspecified targets are your assumptions, not hidden pass criteria.

Failure and boundary behavior

Explain how your guarantees hold in a difficult case relevant to this subject. Address: Non-HTTP protocols? Many clusters?

What to cover

1. 01

   Scope and behavior contract

   Identify users, required behavior and exclusions. Answer: How big? What must the mesh enforce?

2. 02

   State and interfaces

   Define the information owned by the system and the inputs, outputs and errors at its boundaries. Resolve: Latency budget? How fast must changes land?

3. 03

   Capacity and operating targets

   Estimate the dominant workload and resource demand with units and explicit assumptions. For a learned system, also state how quality is measured and what data is available.

4. 04

   Architecture and central flow

   Draw or describe the responsibilities needed for a Service Mesh. Trace a representative request, event or job from its input to a visible result; identify durable state owners.

5. 05

   Failure and boundary walkthrough

   Walk through a difficult case step by step, including detection and recovery. Consider: How are releases made safe? Edge traffic? Non-HTTP protocols? Many clusters?

6. 06

   Tradeoffs and operations

   Compare a credible alternative using your chosen workload and guarantees. Explain a remaining risk, a signal to watch and when you would change the design.

Worked designs

Explore the architecture and decisions, then build on an example with Coach.

Official design

Design a Service Mesh

Discovery, deadlines, bounded retries, ejection, mTLS and telemetry for every call with no app code: a library, then Envoy sidecars fed by xDS, then ambient mode over four clusters. One-hour boards per level, with the theory.

Explore the design

Review rubric

AI feedback uses these criteria. Scores are practice feedback.