Master Amazon SQS in One Page

Source: Dev.to

Introduction

At a buka, nobody is taking your order number. The mama serving jollof doesn’t care who came first; she scoops for whoever is closest, loudest, or holding their plate out farthest. You might wait five minutes while someone who arrived after you gets served first. If you wait patiently, you still get your food, but speed is the whole point.

In contrast, at a bank like GTBank or Access Bank, order matters. You can’t tell the teller to process your withdrawal before your transfer has cleared. Sequence is everything.

This is exactly the difference between Amazon SQS Standard queues and Amazon SQS FIFO queues.

Standard Queues – the “buka” model

• Messages are enqueued and dequeued fast, at scale, in whatever order the system can manage.
• Delivery is not guaranteed to be ordered; a message may be delivered more than once.
• This behavior is intentional—a trade‑off for speed and high throughput.

When to use Standard queues

• Sending OTP notifications to users – order is irrelevant.
• Resizing profile photos after upload – any order works.
• Logging app events for analytics – sequence doesn’t matter.

FIFO Queues – the “bank” model

FIFO (First‑In‑First‑Out) queues guarantee that the first message that enters the queue is the first one processed, every time.

• Exactly‑once processing – no duplicate deliveries.
• Strict ordering – messages are processed in the order they were sent.

Trade‑off

FIFO queues have lower throughput compared to Standard queues; they cannot match the raw volume of a Standard queue.

When to use FIFO queues

• Processing a Paystack or Flutterwave payment – order matters.
• Debiting a wallet after a transaction is confirmed – order matters.
• Running onboarding steps that depend on each other – order matters.

Choosing the right queue

The question isn’t “which one is better?” but rather:

• What happens if two messages arrive in the wrong order or the same message is processed twice?

If the answer is “nothing, we’ll be fine,” go with a Standard queue.
If the answer makes you uncomfortable, choose a FIFO queue.

Most fintech systems operating in Nigeria need FIFO queues, while most notification or media systems can safely use Standard queues.

Conclusion

Understanding your system’s requirements helps you select the appropriate SQS queue type.

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