Neo4j clusters are causally consistent, meaning that by default there is no guarantee a query will be able to read changes made by a previous query. For cases where such a guarantee is necessary, the server provides bookmarks to the client. A bookmark is an abstract token that represents some state of the database. By passing one or multiple bookmarks along with a query, the server will make sure that the query will not get executed before the represented state(s) (or a later state) have been established.

The bookmark manager is an interface used by the driver for keeping track of the bookmarks and this way keeping sessions automatically consistent.

Usage in the session

Enabling it is done by supplying an BookmarkManager implementation instance to this param.
A default implementation could be acquired by calling the factory function neo4j.bookmarkManager().

Warning: Share the same BookmarkManager instance across all session can have a negative impact
on performance since all the queries will wait for the latest changes being propagated across the cluster.
For keeping consistency between a group of queries, use Session for grouping them.
For keeping consistency between a group of sessions, use BookmarkManager instance for grouping them.

const bookmarkManager = neo4j.bookmarkManager()
const linkedSession1 = driver.session({ database:'neo4j', bookmarkManager })
const linkedSession2 = driver.session({ database:'neo4j', bookmarkManager })
const unlinkedSession = driver.session({ database:'neo4j' })

// Creating Driver User
const createUserQueryResult = await linkedSession1.run('CREATE (p:Person {name: $name})', { name: 'Driver User'})

// Reading Driver User will *NOT* wait of the changes being propagated to the server before RUN the query
// So the 'Driver User' person might not exist in the Result
const unlinkedReadResult = await unlinkedSession.run('CREATE (p:Person {name: $name}) RETURN p', { name: 'Driver User'})

// Reading Driver User will wait of the changes being propagated to the server before RUN the query
// So the 'Driver User' person should exist in the Result, unless deleted.
const linkedSession2 = await linkedSession2.run('CREATE (p:Person {name: $name}) RETURN p', { name: 'Driver User'})

await linkedSession1.close()
await linkedSession2.close()
await unlinkedSession.close()