Start with a decision you want to understand, or a complete problem you want to work through. You can take either route without following a fixed course order.
Start with When to add a queue. Follow a PDF upload from a synchronous request to background processing, and see what justifies the change.
At the capacity checkpoint, answer before opening Compare your reasoning. Explain what the queue improves and why it cannot create processing capacity.
Open Design a telemetry ingestion and query service. Establish the requirements, then trace a measurement through the high-level design.
Use the step-through explorer to follow the working path. Before opening a deep dive, explain the bottleneck and propose a change of your own.
Mid, Senior, and Staff+ help you choose your reading depth. All three keep the same correctness requirements. Start where you can explain the working design, then deepen your reasoning.
One decision at three depths: adding a queue
On a standalone guide, Learning depth highlights what to emphasize while keeping the full explanation available.
Inside a question’s Deep dives panel, the level selects a complete explanation for that level. The requirements and baseline high-level design stay shared.
Click or tap the IL Pet character while reading to open guidance for the current section. Choose Why is this important?, How deep should I go?, or What might I be asked?
The Full reading guide gives you the wider study path. Use its section guidance to check what you should be able to explain independently.
Standalone deep-dive articles are public. Full question walkthroughs and the Pet Guide are available with free sign-in.