Fixing false-positive health checks and database load with a simple health check and ElastiCache

SAP-C02 By islever Editorial Last updated

Determine a strategy to improve reliability.

Short answer

BE Point target group health check at a simple HTML page, verify full functionality with Route 53, and add ElastiCache to cut DB load and boost monitoring.

Question

A public retail web application uses an Application Load Balancer (ALB) in front of Amazon EC2 instances running across multiple Availability Zones (AZs) in a Region backed by an Amazon RDS MySQL Multi-AZ deployment. Target group health checks are configured to use HTTP and pointed at the product catalog page. Auto Scaling is configured to maintain the web fleet size based on the ALB health check. Recently, the application experienced an outage. Auto Scaling continuously replaced the instances during the outage. A subsequent investigation determined that the web server metrics were within the normal range, but the database tier was experiencing high load, resulting in severely elevated query response times. Which of the following changes together would remediate these issues while improving monitoring capabilities for the availability and functionality of the entire application stack for future growth? (Choose two.)
  1. Configure read replicas for Amazon RDS MySQL and use the single reader endpoint in the web application to reduce the load on the backend database tier.
  2. Configure the target group health check to point at a simple HTML page instead of a product catalog page and the Amazon Route 53 health check against the product page to evaluate full application functionality. Configure Amazon CloudWatch alarms to notify administrators when the site fails. Correct Answer
  3. Configure the target group health check to use a TCP check of the Amazon EC2 web server and the Amazon Route 53 health check against the product page to evaluate full application functionality. Configure Amazon CloudWatch alarms to notify administrators when the site fails.
  4. Configure an Amazon CloudWatch alarm for Amazon RDS with an action to recover a high-load, impaired RDS instance in the database tier.
  5. Configure an Amazon ElastiCache cluster and place it between the web application and RDS MySQL instances to reduce the load on the backend database tier. Correct Answer

Key Takeaways

A health check must reflect instance health, not backend database health; decoupling it from the DB with a simple page prevents needless instance replacement, while ElastiCache offloads the database tier.

An ALB health check pointed at a DB-dependent product page caused Auto Scaling to replace healthy web instances during a database slowdown. Pointing the target group health check at a simple HTML page while using Route 53 to verify full functionality, plus adding ElastiCache to reduce database load, remediates both the false replacements and the DB bottleneck and improves monitoring.

Common mistake: Relying on read replicas alone (Option A) — the root cause was a health-check false positive causing instance churn, not purely read scaling; the health-check redesign is essential.

Expert Analysis

Why the Answer Is Correct

Option B changes the target group health check to a simple HTML page (so a slow database no longer fails web-instance health and triggers replacement) while a Route 53 health check against the product page monitors true end-to-end functionality, with CloudWatch alarms for notification. Option E adds ElastiCache between the web tier and RDS, reducing database load during spikes.

Why the Other Options Are Wrong

Option A (read replicas) addresses read scaling but not the false-positive health check causing instance churn. Option C's TCP check is weaker than a simple HTTP page for instance health. Option D's RDS recovery alarm does not reduce load or fix the health-check logic.

Community Comment Notes

pangchn (likes 9) selects BE, noting read replicas may not help a non-read-only scenario and that caching reduces data-tier load. michele_scar notes a product catalog benefits from caching. The vote is BE (70) over AB (17).

Official Reference

https://docs.aws.amazon.com/AmazonElastiCache/latest/mem-ug/WhatIs.html

This link opens the official vendor documentation in a new tab.

Community Votes

BE
80%
AB
20%

80% of anonymous learners picked answer BE. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 18 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 18

  1. pangchn 👍 9
    My answer is a bit difference. It doesn't mentioned read-only scnerio so read replica in A may not able to help compare B and C, both pro and con. I lean to B from both the real world and in this particual question to bypass the database
  2. Capt_Leonidas 👍 8
    a public discussion thread on this question
  3. w3ap0nx 👍 5
    "for future growth" -> E (cache in front of the DB)
  4. ovladan 👍 4
    B: Will improve web app D: Will improve database high load issue and query response times.
  5. red_panda 👍 3
    A and B are my answers. A instead of E only because we have no tips that indicate the necessity to have a caching systems. For example, it say "high load on database", but nothing about same record read more more time. So for me A and B
Show 13 more comments
  1. djangoUnchained 👍 3
    B. Health check is failing because the application cannot read from the DB, event though the EC2 instance is fine. As a result the ALB is terminating the EC2 instance unnecessarily.
  2. Dgix 👍 2
    First of all: the instances are terminated because the load on the DB is too high. A: Best way to reduce the load on the DB. It doesn't notify admins, though, which means we then need either B or C (D and E do not notify admins). B: Health checks do not burden the site as they are done relatively seldom, so trying to reduce load by using a page that's lighter on the DB is not very relevant. Notifies admins. C: TCP checks are lighter on the load than HTTP checks, which means the already slight overhead for health checks is reduced further than in B. Notifies admins. This is preferable to B, but both feel inconsequential. D: Recovery actions in this situation are out of scope. This alternative is there to confuse. E: An alternative to A, but it has operational overhead in that the application must be changed to use the cache. A is more straightforward. Thus A and C.
  3. michele_scar 👍 2
    When you talking about a product catalog page, you need to cache information (text, images) to leverage the load on the data tier. ElastiCache is the solution (or a CDN).
  4. failexamonly 👍 2
    read replica to reduce load. tcp check to see if ec2 is reachable
  5. VerRi 👍 2
    TCP check is like a heartbeat check, too rough.
  6. CMMC 👍 1
    Configuring read replicas for Amazon RDS MySQL and using the single reader endpoint in the web application would help distribute the DB workload across multiple instances, and that can alleviate performance issues during high load. Prevent DB-related outages and improve overall application availability. Configuring a CloudWatch alarm for Amazon RDS with an action to recover a high-load, impaired RDS instance in the DB tier enables proactive monitoring and automated recovery in case of DB performance issues. Can trigger automated actions during high load to recover the instance, such as initiating a failover in the Multi-AZ deployment. Ensure that the DB tier remains stable and responsive, reducing the likelihood of application outages.
  7. Dgix 👍 1
    By the way, a public community thread, we get a 503 when submitting voting comments. Please change my previous submission to that type, specifying A and C.
  8. vip2 👍 1
    B and E works as expection. Due to web app is normal, A and C can not help CloudWatch alarm can not support so complicated action
  9. 9f02c8d 👍 1
    A & E is correct answer as the monitoring aspect is not part of the problem statement
  10. titi_r 👍 4
    B and E.
  11. Russs99 👍 3 Answered A
    A and B are my picks
  12. seetpt 👍 3
    BE for me
  13. AWSPro1234 👍 2
    I agree with A and B .

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