Q: Your application connects directly to RDS and at peak load you see `Too many connections` errors. How do you fix this?
Each Lambda invocation or serverless function instance opens its own DB connection. At scale, this exhausts the DB connection limit.
#AWS #RDS & Databases #L2 #Cloud #Infrastructure
🎙️ Candidate Opening & Architectural Context
""When an interviewer asks how I troubleshoot this in AWS, I frame it through my hands-on production experience. When addressing this question, I walk the interviewer through our production incident runbook: isolating the blast radius, checking diagnostic logs and metrics, and applying a safe fix.""
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🛠️ Production Runbook & Step-by-Step Resolution
1️⃣
Initial Diagnostics & Root Cause Analysis
Each Lambda invocation or serverless function instance opens its own DB connection. At scale, this exhausts the DB connection limit.
- Acts as a connection pooler in front of RDS.
- Lambda connects to RDS Proxy (cheap lightweight connection).
- RDS Proxy maintains a small pool of real connections to RDS and reuses them.
2️⃣
Remediation & Permanent Safeguards
Fix: Amazon RDS Proxy For non-Lambda apps: use a connection pool library (PgBouncer for Postgres, ProxySQL for MySQL) to manage connections efficiently. Also: increase the max_connections DB parameter if the instance class supports it.
- DB sees a constant ~20 connections instead of 1000.
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: Acts as a connection pooler in front of RDS.."
⚡ 60-Second Elevator Pitch Talking Points
- Acts as a connection pooler in front of RDS.
- Lambda connects to RDS Proxy (cheap lightweight connection).
- RDS Proxy maintains a small pool of real connections to RDS and reuses them.
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