Map-Reduce Patterns in LangGraph Agent Workflows (ANSWERED)
**Pattern** Planner node outputs list of work items → map workers process each (possibly subgraph) → reducer synthesizes executive summary or ranked list.
TL;DR — Quick Answer
Map phase fans out work items to parallel nodes or dynamic sends; reduce node merges structured results with summarization or voting; enforce concurrency caps and handle stragglers.
The Interview Question
Implement map-reduce in LangGraph: parallel subtasks over items, then aggregate — e.g., analyze 50 PRs.
Deep Explanation
Pattern Planner node outputs list of work items → map workers process each (possibly subgraph) → reducer synthesizes executive summary or ranked list.
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LangGraphMap-ReduceParallelLangChainStartups