LangGraph

Beginner — What are nodes, edges, and state?

• Nodes are steps that perform work, edges choose what runs next, and state carries the information needed by those steps.
• Nodes can be ordinary code or model calls, so the graph can be deterministic or hybrid.

Intermediate — What does a checkpointer do?

• It saves execution progress for later continuation or recovery.
• It is not automatically long-term user memory or a transaction coordinating all external effects.
• Production needs durable storage and authorized thread ownership.

Senior — What makes a graph production-ready?

• Explicit state contracts, safe concurrent updates, durable checkpoints, version migrations, authenticated resume, bounded retries/deadlines, idempotent side effects, and redacted tracing.
• I also define how pending runs survive deployment and how uncertain external writes are reconciled.

Scenario — Resuming an approval sends an email twice. Why?

• The interrupted node may restart, so a send before the interrupt can execute again.
• I move sending behind validated approval into an idempotent business operation and reconcile the send key/receipt on retries.