Reference · Vol. 1 & 2

Key concepts, chapter by chapter

Stateless tier: SONiC daemons keep their durable state in Redis, so a crashed container restarts and rebuilds from the database ( containers ).
Message queue: APPL_DB sits between fpmsyncd and orchagent and absorbs route bursts.
Sharding: multi-ASIC systems run one database/swss/syncd set per ASIC ( multi-ASIC HLD ).
SPOF: on a single switch the database container is a SPOF by design. If it restarts, the dependent services restart too.

Each chapter of System Design Interview (Alex Xu, Vol. 1 & 2) is covered in six parts:

The big picture: what problem the chapter solves and why the design looks the way it does.
Key concepts: the terms you should be able to define.
How it works: the request or data flow, step by step.
Trade-offs: the options, with pros and cons.
Pitfalls & follow-up questions: what interviewers tend to probe.
Acronyms, plus a collapsed "How this relates to SONiC" note. Try to make the connection yourself before you open it.

Use Compact view to show only the concepts and acronyms. An A–Z acronym index is at the bottom.

A–Z acronym index

Acronym	Stands for	Chapter(s)