describe_instances not returning latest state of ec2-instance

[jaimin-sl]

Describe the bug

I have a event rule which calls a lambda when a ec2-instance's state is changed. Rule's instance id list is configured such that it only has on demand instances. Now when I stop/run my instance it changes states as follows
stopped -> pending -> running
running -> stopping -> stopped

In each transition my lambda get's called. Sometime when I do describe_instances(instance_id) (instance_id is provided by event rule) it returns old state of ec2-instance.

For example if I have ran my ec2-instance, lambda should log pending and running in two consecutive logs.
Instead sometimes it logs stopped and pending.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

lambda should log current state of ec2-instance

Current Behavior

Lambda is logging old state of ec2-instance

Reproduction Steps

I am not sure how to reproduce this as sometime this happens and sometimes not,
but here is the minimal code I am using

def lambda_handler(event, context):
    if event['source'] != "aws.ec2":
        print(f"ERROR: Got triggered by {event['Source']}!!")
        return

    instance_id = event['detail']['instance-id']

    #instance data
    instance = ec2_client.describe_instances(InstanceIds=[instance_id])

    if len(instance["Reservations"][0]["Instances"]) != 1:
        print(f'Instance list length is invalid, Length: {len(instance["Reservations"][0]["Instances"])}')
        return

    instance_status = instance["Reservations"][0]["Instances"][0]["State"]["Name"]
    print(f"For {instance_id} state is {instance_status}")

Possible Solution

No response

Additional Information/Context

No response

SDK version used

Python: python3.10, boto3-1.35.95

Environment details (OS name and version, etc.)

Amazon Linux 2023