Dynamically assigning queries to secondary query processing resources

A method, comprising:

• responsive to receiving a query to a database at a first query engine to be performed by the first query engine, evaluating one or more features of the query to determine, by the first query engine, whether the query is eligible to be performed by a second query engine provisioned to perform queries to the database in response to the query or a prior query to the database;
• responsive to a determination that the query is eligible to be performed by the secondary query engine, evaluating, by the first query engine, an availability of the first query engine to perform the query to determine whether to assign the query to be performed by the first query engine or the second query engine;
• assigning, by the first query engine, the query to the second query engine according to the evaluation of the availability indicating that the primary query engine is not available to perform the query;
• and
• causing, by the first query engine, the second query engine to begin performing the query to the database.

One or more non-transitory, computer-readable storage media, storing program instructions that when executed on or across one or more computing devices cause the one or more computing devices to implement:

• responsive to receiving a query to a database at a first query engine to be performed by the first query engine, evaluating, by the first query engine, one or more features of the query to determine eligibility of the query to be performed by a second query engine provisioned to perform queries to the database in response to the query or a prior query to the database;
• responsive to identifying the query as eligible to be performed by the second query engine according to the evaluation of the eligibility of the query, evaluating, by the first query engine, an availability of the first query engine to perform the query;
• assigning, by the first query engine, the query to the second query engine according to the evaluation of the availability of the first query engine indicating that the first query engine is not available to perform the query;
• and
• causing, by the first query engine, the second query engine to begin performing the query to the database.