I have an ECS task that publishes messages to an SNS topic. It is configured with a role that provides all SNS permissions (sns:*). The vast majority of the time, the message is published. However, occasionally at higher volumes, I get an error when trying to publish -

Missing credentials in config, if using AWS_CONFIG_FILE, set AWS_SDK_LOAD_CONFIG=1
    at IncomingMessage.<anonymous> (/app/node_modules/aws-sdk/lib/util.js:904:34)
    at IncomingMessage.emit (events.js:322:22)
    at IncomingMessage.EventEmitter.emit (domain.js:482:12)
    at endReadableNT (_stream_readable.js:1187:12)
    at processTicksAndRejections (internal/process/task_queues.js:84:21)

The only thing I can think of is that there is some sort of throttling happening but I can't find any documentation for why that would be occurring. Has anyone else experienced an issue like this?