You can quickly monitor a variety of resource metrics in the Azure portal in the Metrics view. These metrics enable you to see if a database is approaching the limits of CPU, memory, IO, or storage resources. High DTU, CPU or IO utilization may indicate that your workload needs more resources. It might also indicate that queries need to be optimized.
Also, Query Performance Insight shows the performance in the Azure portal of top consuming and longest running queries for single and pooled databases.
Intelligent Insights for Azure SQL Database and Azure SQL Managed Instance uses built-in intelligence to continuously monitor database usage through artificial intelligence and detect disruptive events that cause poor performance. Intelligent Insights automatically detects performance issues with databases based on query execution wait times, errors, or time-outs. Once detected, a detailed analysis is performed by Intelligent Insights that generates a resource log called SQLInsights
Additionally, you can use Extended Events for advanced monitoring and troubleshooting in SQL Server, Azure SQL Database, and Azure SQL Managed Instance. Extended Events is a "tracing" tool and event architecture, superior to SQL Trace, that enables users to collect as much or as little data as is necessary to troubleshoot or identify a performance problem, while mitigating impact to ongoing application performance.
Query store and automatic tuning should be enabled on your SQL Managed Instance as they help you measure workload performance and automatically mitigate potential performance issues.