What a senior is expected to know and explain

Purpose

Use this set to:

• Audit gaps before a senior / staff interview loop
• Refresh mental models for system design, concurrency, networking, and data
• Prepare crisp explanations: what it is, when you choose it, what breaks, how you diagnose

Assume the reader already ships production software. Content targets explanation quality and judgment, not syntax memorization. Where a concept has a standard JDK or common Java-library implementation, chapters include a Java under the hood section (stdlib internals and client runtimes).

How to use as interview prep

1. Skim the TOC — mark chapters you cannot teach in 5–10 minutes without notes.
2. Read for recall, not comfort — after each chapter, close it and explain aloud: definition → tradeoffs → one production failure story → one interview trap.
3. Prefer tables and decision criteria — interviewers grade decision-making more than vocabulary dumps.
4. Cross-link topics in answers — e.g. thread pools ↔ TCP timeouts ↔ LB health checks; Kafka ↔ DB transactions ↔ exactly-once myths.
5. Drill “what I’d measure / how I’d prove it” — seniors are expected to validate claims with metrics, EXPLAIN, packet captures, GC logs, etc.

Suggested pass order for a time-boxed prep week:

Reading path