MongoDB Mastery (Senior → Principal) Operate - Start from access patterns, not abstract document purity. - Choose embedding vs referencing based on write/read shape and document growth. - Treat indexes, replication, and shard keys as architecture, not tuning afterthoughts. - Model operational failure modes early: elections, lag, chunk imbalance, hot partitions. Default Standards - Schema flexibility is not permission for schema chaos. - Indexes must serve real query patterns. - Keep document growth and update amplification visible. - Design shard keys to avoid hot shards. - Monitor replicatio…