AWS Kinesis has a fairly low write throughput of 1000 writes/sec and 1MB/writes-sec. How does Kinesis enforce this limit? If I were to try to do 1500 writes in a second, would the extra 500 writes be placed into some sort of queue or would they simply fail?
It looks like it simply fails and throws an exception.
An unsuccessfully processed record includes ErrorCode and ErrorMessage values. ErrorCode reflects the type of error and can be one of the following values: ProvisionedThroughputExceededException or InternalFailure. ErrorMessage provides more detailed information about the ProvisionedThroughputExceededException exception including the account ID, stream name, and shard ID of the record that was throttled. For more information about partially successful responses, see Adding Multiple Records with PutRecords in the Amazon Kinesis Data Streams Developer Guide.
https://docs.aws.amazon.com/kinesis/latest/APIReference/API_PutRecords.html
How the rate limiting is done
Rate Limiting The KPL includes a rate limiting feature, which limits per-shard throughput sent from a single producer. Rate limiting is implemented using a token bucket algorithm with separate buckets for both Kinesis Data Streams records and bytes. Each successful write to an Kinesis data stream adds a token (or multiple tokens) to each bucket, up to a certain threshold. This threshold is configurable but by default is set 50% higher than the actual shard limit, to allow shard saturation from a single producer.
You can lower this limit to reduce spamming due to excessive retries. However, the best practice is for each producer is to retry for maximum throughput aggressively and to handle any resulting throttling determined as excessive by expanding the capacity of the stream and implementing an appropriate partition key strategy.
https://docs.aws.amazon.com/streams/latest/dev/kinesis-producer-adv-retries-rate-limiting.html