Neptune openCypher exceptions

When working with openCypher on Amazon Neptune, a variety of exceptions may occur. Below are common exceptions you may receive, either from the HTTPS endpoint or from the Bolt driver (all exceptions from the Bolt driver are reported as Server State Exceptions):

HTTP code	Error message	Retriable?	Remedy
400	(syntax error, propagated directly from the openCypher parser)	No	Correct query syntax, then retry.
500	`Operation terminated (out of memory)`	Yes	Rework the query to add additional filtering criteria to reduce required memory
500	Operation terminated (deadline exceeded)	Yes	Increase the query timeout in the DB cluster parameter group, or retry the request.
500	Operation terminated (cancelled by user)	Yes	Retry the request.
500	Database reset is in progress. Please retry the query after the cluster is available.	Yes	Retry when the reset is completed.
500	Operation failed due to conflicting concurrent operations (please retry). Transactions are currently rolling back.	Yes	Retry using an exponential backoff and retry strategy.
400	`(operation name)` operation/feature unsupported Exception	No	The specified operation is not supported.
400	openCypher update attempted on a read-only replica	No	Change the target end point to the writer end point.
400	MalformedQueryException (Neptune does not show the internal parser state)	No	Correct query syntax and retry.
400	Cannot delete node, because it still has relationships. To delete this node, you must first delete its relationships.	No	Instead of using `MATCH (n) DELETE n` use `MATCH(n) DETACH DELETE(n)`
400	Invalid operation: attempting to remove the last label of a node. A node must have at least one label.	No	Neptune requires all nodes to have at least one label, and if nodes are created without an explicit label, a default label `vertex` is assigned. Change the query and/or application logic so as not to delete the last label. A singleton label of a node can be updated by setting a new label and then removing the old label.
500	Max number of request have breached, ConfiguredQueueCapacity={} for connId = {}	Yes	Currently only 8,192 concurrent requests can be processed, regardless of the stack and protocol.
500	Max connection limit breached.	Yes	Only 1000 concurrent Bolt connections per instance are allowed (for HTTP there is no limit).
400	Expected a [one of: Node, Relationship or Path] and got a Literal	No	Check that you are passing the correct argument(s), correct query syntax, and retry.
400	Property value must be a simple literal. Or: Expected Map for Set properties but didn't find one.	No	A SET clause only accepts simple literals, not composite types.
400	Entity found passed for deletion is not found	No	Check that the entity you are trying to delete exists in the database.
400	User does not have access to the database.	No	Check the policy on the IAM role being used.
400	There is no token passed as part of the request	No	A properly signed token must be passed as part of the query request on an IAM enabled cluster.
400	Error message is propagated.	No	Contact Amazon Support with the Request Id.
500	Operation terminated (internal error)	Yes	Contact Amazon Support with the Request Id.

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