Solve 503 Service Temporarily Unavailable AWS error

"503: Service Temporarily Unavailable" AWS error is triggered when there is an issue with the registered instances or as a result of load balancer.

As part of our Server Support Services at IbmiMedia, We have previously helped to fix numerous AWS related issues for your customers.

In this context, we shall look into why this error occur and how to fix it.

More about AWS error "503: Service Temporarily Unavailable"

The error occurs due to different factors such as;

i. When the surge queue is full.
ii. Load balancer Memory used up will affect the performance level due to poor capacity.
iii. Faulty AWS instances can trigger this error.
iv. If instances are not registered.

Best way to fix AWS error "503: Service Temporarily Unavailable"

Fixing this issue is possible by applying the following tips;

1. Regulating the Surge queue by allowing for enough capacity to improve performance can help fix this issue.  A good approach would be to monitor the SpilloverCount metric.

2. If the Load balancer's memory is full, you should wait for sometime for it to be free again to maintain a good performance level.

3. Ensure that the AWS instance is stable wherever the zone it is running on. You can keep track of it by means of the HealthyHostCount metric.

4. The instance has to be registered in the zone it is running on so as to maintain a good zone load balancing. You can register it by following the instructions below;

i. To begin, Open the Amazon EC2 console via https://console.aws.amazon.com/ec2/
ii. Look at the left pane of the page and click on "Load Balancers" located in the LOAD BALANCING tab.
iii. In this page, choose your load balancer.
iv. Head to the description tab to select Change cross-zone load balancing setting.
v. Now you can enable the Configure Cross-Zone Load Balancing  and click on Save to effect changes.

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Four (4) Methods to solve "503: Service Temporarily Unavailable" in AWS.