Appsync merged api cache doesnt seem to work with source apis, PER_RESOLVER_CACHING and lambda data source.

[danielc92]

Hello, I've set up an appsync merged api with several source apis via aws-cdk (typescript), in a source api I have a lambda datasource with a resolver function, im trying to cache this resolver using PER_RESOLVER_CACHING. Creating a CfnApiCache on the source API does not appear to work. Creating a CfnApiCache on the merged api seems to enable the cache, but doesnt allow me to configure it on the resolver level (I believe it caches the full request). I am looking for a configuration/solution which allows me to flexibly set the cache TTL on each fieldName of each source api. I've also searched rigorously through the AWS Documentation and not able to find something that helps alleviate this problem.

The version of aws-cdk I am using is 2.1029.4

Any help is greatly appreciated thanks.

Note: The CfnApiCache + PER_RESOLVER_CACHING works on a source api that is not associated with any merged api. But as soon as you associate the merged API it ceases to work and there are no cache metrics in cloudwatch.

[yudin-s]

I would verify whether the cache you are enabling belongs to the merged API execution path or only to the source API.

With AppSync merged APIs, the client is executing through the merged API endpoint. Even if the source API resolver has caching configured, that does not necessarily mean the merged API field execution will reuse the source API's resolver cache in the way a direct source API call does.

A few things I would check:

1. Does the merged API itself have API cache enabled?
2. Is the cache config attached to the resolver/field as it exists in the merged API?
3. Do the cache keys include arguments and identity values that actually stay stable?
4. Do CloudWatch cache hit/miss metrics change when you query the merged endpoint directly?

If the same field caches when called via source API but not via merged API, this may simply be an AppSync service limitation rather than a CDK modeling issue.

The pragmatic workaround is to cache at the Lambda/application layer for expensive source fields, especially if the cache key is domain-specific. CDK can express the infrastructure, but it cannot make merged API execution inherit source resolver cache behavior if the service does not apply it there.

[EKOVEEVOKE1]

@yES truly interested @Eyliticrate Ekoveevoke

[EKOVEEVOKE1]

@yES truly interested @Eyliticrate Ekoveevoke

@EKOVEEVOKE1