A company wants to use Alibaba Cloud service to replace their self-built database, which of the following services should it choose?  The best answer is ApsaraDB for RDS, which is a stable, reliable, cost-effective, and scalable online database service that supports most mainstream database engines, including MySQL, SQL Server, PostgreSQL, PPAS (highly compatible with Oracle), and MariaDB 1 .  ApsaraDB for RDS is based on the Apsara Distributed File System and high-performance SSDs of Alibaba Cloud, and provides various features such as backup and recovery, performance monitoring, security, and disaster recovery 2 . By using ApsaraDB for RDS, the company can reduce the complexity and cost of database management, and focus on their core business.

The other options are not suitable for replacing a self-built database. Server Load Balancer (SLB) is a service that distributes traffic among multiple ECS instances according to the configured forwarding rules.  It can be used to balance the load and improve the service availability and fault tolerance of applications 3 . Alibaba Cloud CDN (Content Delivery Network) is a service that delivers content from origin servers to edge nodes, and accelerates the response to user requests.  It can be used to improve the user experience and reduce the bandwidth consumption of origin servers 4 .  Deploying more ECS instances is a way to increase the computing resources and scalability of applications, but it does not provide a database service 5 .  References:   1 : What is ApsaraDB RDS?  - ApsaraDB RDS - Alibaba Cloud 1   2 : ApsaraDB RDS:What is ApsaraDB RDS?  - Alibaba Cloud 2   3 : Server Load Balancer - Alibaba Cloud Documentation Center 3   4 : Alibaba Cloud CDN - Alibaba Cloud 4   5 : Elastic Compute Service (ECS) - Alibaba Cloud 5