1. Measure Before Replacing Outbox Polling

    Evaluate outbox polling with realistic load tests, then consider a simpler application-level delivery path before adopting log tailing.

  2. Separate Shared Counts from Personalized Cache State

    Compose a reaction status from reusable queries, then cache the shared count without leaking one member’s personalized state to everyone else.

  3. Modeling Reactions from Requirements to Scale

    Turn a vague like-button request into a reaction model by clarifying policy, estimating data growth, and planning when count queries must change.

  4. Modernize Legacy Systems Gradually—and Treat Caches as Operations

    Choose legacy boundaries carefully, change them in small steps, and add a shared cache only after DB work and deployment failure modes are understood.

  5. Design Performance Tests from Real Traffic Shapes

    Estimate volume and arrival patterns before choosing a load test, add deliberate headroom, and require evidence only where traffic risk justifies it.

  6. You Can Practice High-Traffic Engineering Without Real Traffic

    Build and operate a small service, create load deliberately, and show how you found and fixed bottlenecks without pretending a load test equals production experience.