MongoDB DBA Associate key terms

A group of mongod processes that maintain the same data set. One member is primary and accepts writes; secondaries replicate the primary's oplog and can become primary after an election.

A capped collection in the local database that records all data-modifying operations. Secondaries tail it to replicate changes and to catch up after network partitions or restarts.

The process by which replica set members vote to choose a new primary when the current primary is unavailable. Requires a majority of voting members and uses a term number to order attempts.

A replica set member that participates in elections but holds no data and cannot become primary. Used to provide a voting majority without the cost of an extra data-bearing node.

A replica set configuration value that influences which secondary is most likely to be elected primary. Higher values win; a priority of 0 marks a member as unable to become primary.

The level of acknowledgment requested from MongoDB for a write operation. Options include w:1, w:majority, and w:0 (fire-and-forget), balancing durability against latency.

A client setting that routes read operations to specific replica set members, such as primary, primaryPreferred, secondary, or nearest. Affects consistency and read latency.

The process by which a new replica set member copies the full data set from an existing member and then applies oplog entries to catch up. It can be time-consuming and I/O intensive.

A replica set member that is invisible to client applications and cannot become primary. It can still vote in elections and is often used for dedicated backup or reporting workloads.

A replica set member that applies oplog entries after a configured delay, maintaining a historical snapshot. Useful for recovering from accidental data deletion or corruption.

A MongoDB deployment architecture that distributes data across multiple shards to support horizontal scaling. It consists of shards, config servers, and mongos routers.

One or more indexed fields that determine how documents are distributed across shards in a sharded cluster. Choosing a good shard key is critical for even data distribution and query targeting.

A contiguous range of shard key values stored on a single shard. The balancer migrates chunks between shards to keep data evenly distributed.

A background process in a sharded cluster that monitors chunk distribution and migrates chunks between shards to balance data. It can be stopped during maintenance windows.

A routing service for sharded clusters. It receives client requests, determines which shard(s) hold the required data using the config servers' metadata, and aggregates results.

A replica set that stores metadata about the sharded cluster, including chunk ranges and shard locations. In modern versions it must run as a replica set (CSRS).

A shard key that uses a hash of a field value to distribute documents evenly across shards. It provides good write distribution but poor range-query targeting.

The default storage engine for MongoDB since version 3.2. It provides document-level concurrency control, compression, and checkpointing for durability.

A WiredTiger operation that flushes modified data from memory to disk, creating a consistent on-disk snapshot. Checkpoints occur at intervals and on clean shutdown.

A write-ahead logging mechanism that ensures durability by recording changes in a journal before applying them to data files. Enabled by default in WiredTiger.

A WiredTiger feature that reduces storage footprint by compressing data and indexes. Supported algorithms include snappy, zlib, and zstd, configurable per collection or globally.

Salted Challenge Response Authentication Mechanism, the default authentication method in MongoDB. It verifies user identity using a username and password without transmitting the password in clear text.

A MongoDB authentication method that uses TLS client certificates to verify identity. Often used for internal member authentication in replica sets and sharded clusters.

MongoDB's authorization model where privileges are grouped into roles, and roles are assigned to users. Built-in roles cover common needs; custom roles can be defined.

Transport Layer Security, used to encrypt network traffic between MongoDB clients and servers, and between cluster members. Requires configuring certificates and CA files.

Protection of stored data by encrypting database files. MongoDB Enterprise offers native encryption at rest using WiredTiger and a key management service.

A command-line utility that creates a binary export of a MongoDB database's contents. It is often used for backups and can target a specific database or collection.

A command-line utility that loads data from a binary dump created by mongodump into a MongoDB instance. It can replay oplog entries for point-in-time recovery.

The process of restoring a backup and then replaying oplog entries up to a specific moment, allowing recovery from accidental data loss or corruption.

The modern MongoDB Shell, a JavaScript-based interactive interface for administering and querying MongoDB deployments. It replaces the legacy mongo shell.

MongoDB's on-premises management platform for monitoring, backing up, and automating MongoDB deployments. It provides a web interface and agents for automation.

A hosted MongoDB management service for monitoring, backup, and automation. It is similar to Ops Manager but delivered as a cloud service.

A MongoDB feature that records slow or all operations to the system.profile collection. Used to diagnose performance issues and identify inefficient queries.

A diagnostic output that shows how MongoDB executes a query, including index usage, documents examined, and execution stages. Helps optimize query performance.

A data structure that improves the speed of read operations by allowing MongoDB to locate documents without scanning the entire collection. Common types include single-field, compound, and multikey.

A maintenance procedure that upgrades replica set members one at a time, maintaining availability. It typically involves upgrading secondaries before the primary.

Feature Compatibility Version, a setting that controls which features are available and ensures compatibility during upgrades. It must be set appropriately before and after version upgrades.