Kinesis Data Stream via API Gateway: Observed 100k+ Records/Second. Investigating Unexpected Throughput.

I'm observing unexpectedly high throughput for my Kinesis Data Stream integration with API Gateway, and I'm seeking clarification on the metrics and possible explanations.

Setup:

• Using Kinesis Data Stream with API Gateway REST API integration for PutRecords
• Kinesis Data Stream: 8 shards, provisioned mode
• API Gateway: Burst limit and rate limit both set to 5000

Expected behavior: Based on my understanding, each Kinesis shard can process 1000 records per second. With 8 shards, I expected a maximum throughput of 8000 records per second.

Observed behavior:

• CloudWatch metrics for API Gateway's Count (1-second sum) exceed 100,000
• Kinesis PutRecords' Records sum (1-second sum) also exceeds 100,000
• No rate limiting or throttling events recorded for either Kinesis or API Gateway during this period

Questions:

1. Am I misinterpreting the meaning of these metrics?
2. How is it possible to achieve such high throughput given the setup described above?
3. Are there any factors I'm overlooking that could explain this behavior?

I've attached screenshots of the relevant CloudWatch metrics for reference.

Any insights or explanations would be greatly appreciated. Thank you in advance for your help!

Kinesis PutRecords.Records

API GW Count

Kinesis Throttling History