A high-throughput API ingestion service runs on Amazon EC2 instances inside an Auto Scalin… — AWS Certified Solutions Architect - Professional

A high-throughput API ingestion service runs on Amazon EC2 instances inside an Auto Scaling group (ASG) deployed across $3$ Availability Zones ( $AZ-A$ , $AZ-B$ , and $AZ-C$ ). The instances reside in private subnets, and the ASG is placed behind an Application Load Balancer (ALB). The application instances require custom configuration scripts during launch, resulting in a total initialization and bootstrapping time of $360$ seconds before they can register as healthy targets. The platform experiences two major operational issues: first, every day at exactly $08:00$ UTC, a scheduled partner integration triggers a massive, instantaneous influx of API requests, causing immediate HTTP $503$ (Service Unavailable) errors on the ALB for the first $10$ minutes; second, during scaling activities, the ASG frequently launches more instances than required, leading to unnecessary costs. Furthermore, a recent outage in $AZ-A$ prevented instances in $AZ-B$ and $AZ-C$ from making outbound licensing API calls, which are routed through a single NAT Gateway located in $AZ-A$ . Which combination of actions should a Solutions Architect implement to address these scaling, reliability, and cost issues?

A
Deploy a secondary NAT Gateway in $AZ-B$ and update the route tables of the private subnets in $AZ-B$ and $AZ-C$ to use the new NAT Gateway. Configure a scheduled scaling action to scale out the Auto Scaling group $15$ minutes before $08:00$ UTC, and request AWS Support to pre-warm the Application Load Balancer for the anticipated daily spike. Set the default cooldown and instance warmup periods on the Auto Scaling group to $400$ seconds.
Deploy a NAT Gateway in each Availability Zone and update the route tables of each private subnet to direct outbound internet traffic to the NAT Gateway in its own zone. Configure a scheduled scaling action to scale out the Auto Scaling group $15$ minutes before $08:00$ UTC, and request AWS Support to pre-warm the Application Load Balancer for the anticipated daily spike. Set the default cooldown and instance warmup periods on the Auto Scaling group to $400$ seconds.Answer
C
Deploy a NAT Gateway in each Availability Zone and update the route tables of each private subnet to direct outbound internet traffic to the NAT Gateway in its own zone. Configure a scheduled scaling action to scale out the Auto Scaling group $15$ minutes before $08:00$ UTC, and request AWS Support to pre-warm the Application Load Balancer for the anticipated daily spike. Set the default cooldown and instance warmup periods on the Auto Scaling group to $180$ seconds.
D
Deploy a NAT Gateway in each Availability Zone and update the route tables of each private subnet to direct outbound internet traffic to the NAT Gateway in its own zone. Configure a target tracking scaling policy based on the average CPU utilization metric with a target value of $60\%$ , and set the instance warmup time to $400$ seconds. Set the default cooldown period to $400$ seconds.

Answer

Deploy a NAT Gateway in each Availability Zone and update the route tables of each private subnet to direct outbound internet traffic to the NAT Gateway in its own zone. Configure a scheduled scaling action to scale out the Auto Scaling group

15

minutes before

08:00

UTC, and request AWS Support to pre-warm the Application Load Balancer for the anticipated daily spike. Set the default cooldown and instance warmup periods on the Auto Scaling group to

400

seconds.

The correct response resolves all specified requirements. By deploying a NAT Gateway in each of the three Availability Zones, egress traffic is fully isolated at the zone level, ensuring that an outage in one zone does not disrupt licensing API calls in the others. Requesting AWS Support to pre-warm the Application Load Balancer and configuring a scheduled scaling policy to scale out the Auto Scaling group

15

minutes before

08:00

UTC ensures that both the load balancer and the targets (which take

360

seconds to bootstrap) are ready before the predictable spike occurs, eliminating HTTP

503

errors. Finally, adjusting the cooldown and instance warmup periods to

400

seconds (which is greater than the

360

-second initialization duration) ensures the Auto Scaling group waits for newly launched instances to become healthy and start reporting metrics before evaluating further scaling actions, preventing over-provisioning.

Step-by-Step Solution

Configure egress redundancy by provisioning a NAT Gateway in each of the three Availability Zones (

AZ-A

AZ-B

, and

AZ-C

Three separate NAT Gateways are active across the three zones.

This removes the single point of failure by ensuring that an outage in one zone does not affect internet-bound traffic from instances in other zones.

Configure route tables in each zone to point internet-bound traffic (

0.0.0.0/0

) to the NAT Gateway residing within the corresponding Availability Zone.

Outbound traffic from each subnet is localized to its respective Availability Zone.

This establishes fault isolation and eliminates cross-zone routing dependencies.

Submit a support ticket to AWS to pre-warm the Application Load Balancer in preparation for the daily

08:00

UTC traffic burst.

The Application Load Balancer is pre-scaled to handle the sudden, massive volume of requests.

Application Load Balancers scale gradually; a massive, instantaneous surge will result in HTTP

503

errors unless the load balancer is pre-warmed.

Establish a scheduled scaling policy to scale out the Auto Scaling group

15

minutes prior to the

08:00

UTC surge, and set the default cooldown and instance warmup to

400

seconds.

Instances are launched, fully bootstrapped, and healthy before the spike begins, and the Auto Scaling group does not launch redundant instances.

15

-minute buffer allows the

360

-second bootstrapping process to finish. Ensuring the warmup and cooldown periods exceed

360

seconds prevents metric lag from triggering unnecessary secondary scale-out actions.

Key Concept

Configuring resilient egress architecture, pre-warming load balancers for flash traffic, and aligning Auto Scaling cooldown periods with instance initialization times.

Estimated Time:3m 0s

Question

Answer

Step-by-Step Solution

Key Concept

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