You can now enable checking for field- and object-level security permissions on SOQL SELECT queries by using the WITH SECURITY_ENFORCED clause. New OrgLimit and OrgLimits Apex classes include methods to obtain a list or map of all OrgLimit instances, such as SOAP API requests, Bulk API requests, and Streaming API limits. A new System.SObject.isSet() method checks whether a field was queried or set by an Apex assignment. A new Apex Unexpected Exception event type is added to the EventLogFile object.
For more information on these enhancements, see the Apex Developer Guide.