Amazon SQS
Fully managed message queuing service for decoupling distributed components.
Key facts
- Producers write, consumers poll and delete — neither side needs the other online
- Standard: near-unlimited throughput, at-least-once, best-effort ordering
- FIFO: strict ordering, exactly-once processing, lower throughput
- Limits: 256 KB max message size, 14-day max retention, 20s long polling
Ad slot 1 · 728×90 / 320×100
Exam triggers
- "Decouple", "buffer", "smooth out traffic spikes", "process asynchronously"
- Work must not be lost when a component fails → SQS + DLQ
- Order matters / no duplicates → FIFO, not Standard
- Consumers overwhelmed by bursty producers → SQS between them
Not this service →
- One message to many subscribers → SNS
- Replay or multiple independent readers → Kinesis Data Streams
In production
what the exam skips
- At-least-once means idempotency isn't optional — every handler needs a dedupe key and a store to check it against
- Visibility timeout shorter than processing time is a silent double-execution bug that only appears under load
- With Lambda, one bad message retries the whole batch unless partial batch response is enabled
- Nobody monitors the DLQ — alarm on its visible message count or find 40k dead messages during an unrelated incident
- 256 KB is smaller than it sounds — payloads need the S3 pointer pattern
Ad slot 2 · 336×280 / 300×250
Commonly confused with
Practice questions
Verification pending — not yet checked against AWS documentation.