In that case, Atatus is affordable in my opinion.

For server monitoring, Have a look at Prometheus, Grafana, Zabbix

Ofcourse, If your business is growing, chances are, you are collecting more and more logs. Your log management process is ultimately slowing down your troubleshooting. Atatus provides you with hassle-free log management delivered as a fully managed cloud service. You don't have to set up and maintain it. This instantly cuts costs, reduces IT load and improves both the speed of troubleshooting and resolution of issues.

We use Atatus, that can help with application performance troubleshooting and optimization, helping us to identify slow database queries and optimize query performance.

With Atatus, your teams can identify and fix slow page loads, route changes, poor performance of static assets, JS errors, client side logging for every user including long load times, specific errors, asset performance, web vitals, DNS, SSL connection from a single pane of glass.

Similarly, Atatus Infrastructure monitoring has been nice for us

Atatus is an alternative to Grafana - open source observability platform. However, open source is not always user-friendly when it comes to alerts and charts

Atatus Real User Monitoring can definitely help you to identify frontend errors and fix them when it is so unstable

Atatus provides dashboards and alerting for monitoring your servers, software and more in order to understand how healthy your systems are.

First find out why it is slow. If you are not aware of the reason and also the performance got worse, go for any APM solutions that suits your requirement. Atatus has been doing a great job in monitoring with real time insights lately.