• What are multi-document ACID transactions in MongoDB?

  • How do transactions work in replica sets?

  • How do transactions work in sharded clusters?

  • What are limitations of MongoDB transactions?

  • Explain MongoDB replication architecture in detail

  • What happens during replica set elections?

  • What is majority write concern?

  • How does MongoDB ensure durability?

  • WiredTiger vs MMAPv1 – deep comparison

  • How does MongoDB handle concurrency?

  • What is document-level locking?

  • How does WiredTiger cache work?

  • How does MongoDB manage memory?

  • What is MapReduce and when should it be avoided?

  • MapReduce vs Aggregation Framework

  • How does full-text search work in MongoDB?

  • What is a text index?

  • What is Atlas Search?

  • How does MongoDB handle large file storage?

  • GridFS internal working

  • What is mongos?

  • Role of config servers

  • How does query routing work in sharded clusters?

  • How do you reshard a collection?

  • What are common shard key design mistakes?

  • How do you migrate data from SQL to MongoDB?

  • How do you perform rolling upgrades?

  • Zero-downtime MongoDB upgrade strategy

  • How do you secure MongoDB in production?

  • Authentication mechanisms in MongoDB

  • Role-based access control (RBAC)

  • How does TLS/SSL work in MongoDB?

  • How does MongoDB handle disaster recovery?

  • How do you troubleshoot slow queries?

  • How does MongoDB handle high write throughput?

  • MongoDB in microservices architecture

  • One database per service – pros & cons

  • MongoDB with containers & Kubernetes

  • How does MongoDB handle schema evolution?

  • Common production deployment best practices