Web search only becomes interesting when you scale it up. At small scale it's just fetching pages and tying together library code, which is fine but not particularly interesting or educational. Once you scale up, though, it involves tons of complicated and fascinating topics (math, distributed systems, compression, networking, query planning, databases, etc.). You also start having to make trade-offs among features, which is often a good sign that a problem is complex enough to be worthy of your time.