MongoDB Associate DBA - Fact Sheet¶

Exam Overview¶

Exam Name: MongoDB Associate DBA Duration: 75 minutes Questions: 62 multiple-choice questions Passing Score: 65% Cost: $150 USD Valid For: 3 years Delivery: Online proctored

📖 Official Certification Page - Registration and details 📖 MongoDB Administration Docs - Admin reference 📖 MongoDB University - Free learning resources

Target Audience¶

This certification is designed for: - Database administrators managing MongoDB deployments - System administrators responsible for MongoDB infrastructure - DevOps engineers deploying and maintaining MongoDB - Site reliability engineers ensuring MongoDB availability - Professionals with 6+ months MongoDB administration experience

Exam Domains¶

Domain 1: Server Administration (25%)¶

mongod Configuration:

# mongod.conf
storage:
  dbPath: /var/lib/mongodb
  journal:
    enabled: true
  wiredTiger:
    engineConfig:
      cacheSizeGB: 4
    collectionConfig:
      blockCompressor: snappy

systemLog:
  destination: file
  path: /var/log/mongodb/mongod.log
  logAppend: true

net:
  port: 27017
  bindIp: 0.0.0.0

processManagement:
  fork: true

WiredTiger Storage Engine: - Default storage engine since MongoDB 3.2 - Document-level concurrency control - Compression: snappy (default), zlib, zstd, none - Cache size: max(256 MB, 50% of RAM - 1 GB) by default - Checkpoint interval: 60 seconds - Journal: write-ahead log for durability

Key Server Commands: - db.serverStatus() - Comprehensive server metrics - db.stats() - Database statistics - db.collection.stats() - Collection statistics - db.currentOp() - Currently running operations - db.killOp(opId) - Kill a running operation

📖 mongod Reference - mongod documentation

Domain 2: Replication (20%)¶

Replica Set Configuration:

rs.initiate({
  _id: "myReplicaSet",
  members: [
    { _id: 0, host: "mongo1:27017", priority: 2 },
    { _id: 1, host: "mongo2:27017", priority: 1 },
    { _id: 2, host: "mongo3:27017", priority: 1 }
  ]
});

Member Types: | Type | Votes | Can be Primary | Data | Purpose | |------|-------|---------------|------|---------| | Primary | 1 | Yes | Full | Read/write | | Secondary | 1 | Yes | Full | Read replicas | | Arbiter | 1 | No | None | Tiebreaker | | Hidden | 1 | No | Full | Backup/reporting | | Delayed | 1 | No | Full (delayed) | Rolling backup | | Priority 0 | 1 | No | Full | Never primary |

Read Preferences: | Mode | Description | |------|-------------| | primary | Read from primary only (default) | | primaryPreferred | Primary, fallback to secondary | | secondary | Read from secondary only | | secondaryPreferred | Secondary, fallback to primary | | nearest | Lowest latency member |

Write Concerns: | Setting | Description | |---------|-------------| | w: 1 | Primary acknowledgment (default) | | w: "majority" | Majority of voting members | | w: <number> | Specific number of members | | j: true | Wait for journal commit |

📖 Replication - Replication documentation

Domain 3: Sharding (20%)¶

Shard Key Selection Criteria: - High cardinality - Many unique values - Low frequency - Values are evenly distributed - Non-monotonic - Avoids hotspotting on one shard - Supports query patterns - Included in common queries

Sharding Types:

Sharding Commands:

// Enable sharding on database
sh.enableSharding("mydb");

// Shard a collection (ranged)
sh.shardCollection("mydb.orders", { customerId: 1 });

// Shard a collection (hashed)
sh.shardCollection("mydb.events", { eventId: "hashed" });

// Check sharding status
sh.status();

📖 Sharding - Sharding documentation

Domain 4: Security (15%)¶

Authentication Methods: | Method | Description | |--------|-------------| | SCRAM-SHA-256 | Default, password-based | | x.509 | Certificate-based | | LDAP | External directory service | | Kerberos | Enterprise authentication |

Built-in Roles:

📖 Security - Security documentation

Domain 5: Backup and Recovery (10%)¶

Backup Methods: | Method | Type | Consistent | Impact | |--------|------|------------|--------| | mongodump | Logical | Point-in-time with oplog | Some load | | Filesystem snapshot | Physical | Yes (with journaling) | Low | | Atlas Backup | Cloud | Continuous | None | | Ops Manager | Managed | Continuous | Minimal |

📖 Backup Methods - Backup documentation

Domain 6: Monitoring (10%)¶

Key Monitoring Tools: - mongostat - Real-time server statistics - mongotop - Per-collection read/write time - db.serverStatus() - Comprehensive metrics - db.currentOp() - Running operations - Database Profiler - Slow query analysis

Critical Metrics:

📖 Monitoring - Monitoring documentation

Key Defaults to Remember¶