Boost MongoDB Performance: Read/Write Strategies, Authentication, and Replica Set Tips

MongoDB Read Preference Strategies

MongoDB provides several read preference modes to control which replica set members are used for read operations:

RP_PRIMARY

RP_PRIMARY_PREFERRED

RP_SECONDARY

RP_SECONDARY_PREFERRED

RP_NEAREST

Choose a mode based on consistency requirements and write load: use primary‑preferred for strong consistency, secondary‑preferred when reads dominate, or the default nearest when no specific preference is needed.

Example Configuration (PHP)

<code>$options = array(
    'replicaSet' => $replicaSet,
    'username'   => $username,
    'password'   => $password,
    'readPreference' => MongoClient::RP_SECONDARY
);
</code>

MongoDB Write Concerns

The default write concern for the legacy MongoClient driver is w=1 (acknowledged), which ensures data is written to the primary's journal. Setting w=0 maximizes throughput but provides no durability guarantee. You can also specify w=N to require acknowledgment from N replica set members.

MongoDB Authentication

For security, enable authentication and use the admin database for user management. The command‑line login format is:

<code>$mongo -uusername -ppassword ip:port/admin</code>

When using the PHP driver, the driver defaults to the admin database, so no extra configuration is needed.

Replica Set Configuration

If your deployment is a replica set, include the replicaSet parameter in the connection options; otherwise the driver will raise errors such as “not master”. Example of a missing parameter causing intermittent failures because the driver may connect to a secondary for writes.

For single‑node or MongoS deployments, omit the replicaSet option.

Connection Best Practices

Avoid creating a new MongoClient for each request. Instantiate a single client and reuse it for multiple read/write operations to prevent connection churn, especially when traffic passes through load balancers (LVS).

In high‑traffic scenarios, excessive client creation can exhaust connection limits and cause timeouts, dramatically degrading performance.