Lambda spike connection rejected
Your product runs as AWS Lambda functions (Node.js) talking directly to an RDS Postgres instance (max_connections=200). A marketing email went out at noon and traffic spiked 8x. The API starts returning 500s with 'remaining connection slots are reserved' / 'too many clients already'. CloudWatch shows Lambda concurrency briefly hit 600. The DB CPU is only at 40%. How do you triage and mitigate, and what's the right architecture?
What a strong answer looks like
Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.
0:00 of about 30 min
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.