Embodiments of the present technology relate managing database query concurrency. A method of the present technology can include receiving a query, generating a first query plan that can be used to execute the query in system memory without any system memory constraints, and estimating a system memory cost for executing the query in the system memory using the first query plan. The method can also include placing the query in a queue if available system memory does not satisfy the estimated system memory cost. The method can further include conditionally selecting the query from the queue, conditionally generating a second query plan for the query that can be used to execute the query in the system memory in compliance with a system memory constraint, and conditionally executing the query in the system memory.