Notes on Magento

In MongoDB, primary nodes are the node that can accept write. These are also known as master nodes. The replication in MongoDB is single master so, only one node can accept write operations at a time. Secondary nodes are known as slave nodes. These are read only nodes that replicate from the primary. In MongoDB, … Read more

A replica can be specified as a group of mongo instances that host the same data set. In a replica set, one node is primary, and another is secondary. All data is replicated from primary to secondary nodes. In MongoDB, a replica set is a group of MongoDB servers that maintain the same data set, … Read more

Covered query makes the execution of the query faster because indexes are stored in RAM or sequentially located on disk. It makes the execution of the query faster. Covered query makes the fields are covered in the index itself, MongoDB can match the query condition as well as return the result fields using the same … Read more

A query is called covered query if satisfies the following two conditions: The fields used in the query are part of an index used in the query. The fields returned in the results are in the same index. A covered query in MongoDB refers to a query where all the fields used in the query … Read more

If a shard is down and you even do query then your query will be returned with an error unless you set a partial query option. But if a shard is slow them Mongos will wait for them till response. In MongoDB, if a shard is down or slow and you perform a query, the … Read more