Advanced Questions

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Level: Advanced

🔴 Complex Scenarios & Architecture.

Tackle high-level design, production-grade scaling, security, and advanced internals.

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1. How can you automatically remediate a "Security Group allowing SSH from 0.0.0.0/0" finding?

Use AWS Config to detect the violation and trigger an SSM Automation Document (Remediation Action) to remove the rule.

Automated remediation (Self-healing compliance) is a key SysOps maturity indicator.

2. What is "EventBridge" (formerly CloudWatch Events) primarily used for in SysOps?

To build event-driven architectures (e.g., "If EC2 terminates, trigger Lambda") or schedule periodic tasks (Cron).

It acts as the central nervous system, routing operational events to targets.

3. How do you implement "Cross-Region Replication" (CRR) for an S3 bucket with existing objects?

Enable CRR on the bucket (for new objects), then use S3 Batch Operations to replicate the existing objects.

Turning on CRR only affects future uploads; Batch Ops handles the backlog.

4. What is the "Unified CloudWatch Agent"?

A single agent that collects both system metrics (Memory, Disk) and application logs from EC2 instances and on-premise servers.

It replaces the legacy Perl scripts and provides a unified config file (amazon-cloudwatch-agent.json).

5. How do you debug an "Access Denied" error when an EC2 instance tries to access S3?

Check the IAM Role attached to the instance and the S3 Bucket Policy (and potentially SCPs or VPC Endpoint Policies).

S3 authorization is the intersection of Identity Policies and Resource Policies.

6. What is "AWS Control Tower"?

A service that automates the setup of a landing zone (multi-account environment) based on best practices, enforcing guardrails via SCPs and Config.

It is the prescriptive way to set up AWS Organizations securely.

7. How do you interpret a "SpilloverCount" metric on a Classic Load Balancer?

The Surge Queue is full (1024 requests), and the LB is rejecting new requests with HTTP 503. Backend is too slow or down.

This means you are dropping traffic. Scale the backend immediately.

8. What is "AWS Health Aware" automation?

Using EventBridge to listen for AWS Health events (e.g., "EBS Volume Lost") and triggering automation to mitigate impact (failover).

Proactive automation can handle hardware degradation before it becomes an outage.

9. How can you ensure that an Auto Scaling Group (ASG) replaces an unhealthy instance immediately?

Configure the ASG to use ELB Health Checks. If the ELB marks it unhealthy (failed HTTP check), the ASG terminates and replaces it.

By default, ASG only checks EC2 Status (hardware). ELB checks ensure the app is working.

10. What is "OpsCenter" in Systems Manager?

A central location to view, investigate, and resolve operational issues (OpsItems) tailored to specific AWS resources.

It aggregates findings from Config, CloudWatch, and Security Hub.

11. How do you analyze "Cost and Usage Reports" (CUR) effectively?

Configure CUR to deliver CSV/Parquet files to S3, then use Amazon Athena to query the data with SQL.

CUR files are often too large for spreadsheets; Athena allows deep granular analysis.

12. What happens if you lose the MFA device for the root user?

You must go through the "Troubleshoot MFA" process, verifying identity via email and phone call (and potentially identity documents).

Always have a backup operational procedure for root access recovery.

13. How do you troubleshoot a Lambda function timing out?

Check logs for "Task timed out", check if downstream services (DB, API) are slow, and consider increasing the timeout setting or memory (which increases CPU/Network).

More memory = More CPU in Lambda. Sometimes "Throwing hardware at it" works.

14. What is "VPC Flow Logs" format?

A space-separated string containing timestamp, source IP, dest IP, port, protocol, packets, bytes, start/end time, and action (ACCEPT/REJECT).

Knowing the format helps when writing Athena queries to parse logs.

15. How do you securely manage " SSH keys" for a team of 50 developers?

Do not use SSH keys. Use Session Manager (IAM auth) instead. If you must, use EC2 Instance Connect to push temporary keys.

Static long-lived SSH keys are a major security liability (rotation is hard).

16. What is "AWS X-Ray"?

A service to analyze and debug distributed applications (Trace requests through Application -> Lambda -> DynamoDB).

X-Ray visualizes the latency contribution of each hop in the chain.

17. What is the "SurgeQueueLength" metric?

The number of pending requests waiting for a backend instance to become free. High values indicate backend saturation.

If the queue fills up, Spillover occurs.

18. How do you recover from an accidental deletion of a KMS Key (CMK)?

You can cancel the deletion within the "Pending Deletion" window (7-30 days). If the window passes, data encrypted with that key is permanently lost.

KMS keys are the one thing AWS Support cannot recover if fully deleted.

19. What is "RAM" (Resource Access Manager)?

A service to securely share AWS resources (Subnets, Transit Gateways, License configs) across AWS accounts.

Sharing subnets allows "VPC Sharing" where the Network team manages the VPC, and Dev teams just see subnets to deploy into.

20. How do you handle "Disk Full" on a Linux instance without stopping it?

Identify large files (du -h), delete/compress/move them. If unrelated, modify EBS volume size in console, then growpart and resize2fs.

You can grow an attached volume while the OS is running and IO is happening.

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