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Chapter 7

When Things Get Busy

Metaphor: A busy café or post office Mental image: “More helpers, same rules.”

Key Ideas

This chapter addresses scale — what happens when many people want the same thing at the same time.

Core concepts to cover:

  1. One server has limits

    • Like one librarian can only help so many people at once
    • CPU, memory, network bandwidth — all finite
    • At some point, requests start waiting or failing

  2. The solution isn’t magic — it’s multiplication

    • Run more than one server
    • Each handles a portion of the requests
    • The rules don’t change, just the number of workers

  3. Load balancing: the traffic director

    • A load balancer distributes incoming requests across servers
    • Round-robin, least connections, or smarter algorithms
    • This is often what a reverse proxy does (revisit Chapter 5)

  4. Horizontal vs. vertical scaling

    • Vertical: make one server bigger (more RAM, faster CPU)
    • Horizontal: add more servers
    • Horizontal is usually more resilient and cost-effective at scale

  5. Caching: answering without asking

    • Some responses don’t change often
    • Cache them at the edge (CDN, reverse proxy)
    • Serve the cached copy instead of bothering the origin server
    • Metaphor: photocopying popular books instead of fetching from the archive each time

  6. CDNs: servers closer to you

    • Content Delivery Networks: copies of your content distributed globally
    • When you request a page, you get it from a server nearby
    • Faster responses, less load on the origin

  7. Resilience: what if one server fails?

    • With multiple servers, one can fail and the others continue
    • Health checks: the load balancer pings servers to ensure they’re alive
    • Graceful degradation vs. total outage

Tone for this chapter

Practical and demystifying. Scale shouldn’t sound like a problem only “big tech” faces. Even small sites benefit from understanding these concepts. The metaphors (café, post office) should keep it grounded.

Bridge to Chapter 8

We’ve covered how the web works at scale. But what about your corner of it? The final chapter brings it back to the reader — running and owning your own piece of the web.

Status: Work in progress