AWS Lambda not able to connect to public RDS instance


I have a public RDS instance running postgres. I can connect to it from my local host. The same function fails when I try to run it on lambda. The error I get is

***could not translate host name <RDS_HOST_NAME> to address: Name or service not known\n"

There is no VPC associated with the lambda function. I can connect using psq -h <RDS_HOST_NAME> from my machine. Could you please suggest on how to resolve this?

  • Are you using the public RDS endpoint as host name? (....<region>

  • Yes.. it is <dbname>.<...>

1 Answer

I had a similar problem, which I solved with the following steps.

I created a new RDS instance in the management console. At this time, I specified that a new VPC, subnet group, and security group be created as well.

In this case, a rule was created with the source IP "" as an inbound rule for the security group. In this state, I could still connect from the local PC, but not from Lambda. When I changed the source IP to, I was able to connect from Lambda.

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answered 2 years ago

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