Ensuring Ordered Order Processing with SQS FIFO
Answer
Correct answer: B — Integrate the API Gateway REST API with an Amazon SQS FIFO queue that invokes AWS Lambda, guaranteeing orders are processed in arrival order.
A company is building an ecommerce web application on AWS. The application sends information about new orders to an Amazon API Gateway REST API to process. The company wants to ensure that orders are processed in the order that they are received. Which solution will meet these requirements?
Community Insight
The question tests whether you can recognize that strict ordering requires an SQS FIFO queue, and the trap is picking a standard queue or SNS topic that provide no ordering guarantee at all.
This SAA-C03 question asks how an ecommerce application can guarantee that orders arriving through an Amazon API Gateway REST API are processed in exact arrival order. The correct design routes each order from an API Gateway integration into an Amazon SQS FIFO queue whose queue trigger invokes AWS Lambda, because FIFO queues are the only option listed that preserves strict first-in, first-out ordering.
Option D is the most tempting wrong answer: an SQS standard queue with Lambda invocation looks architecturally identical, but standard queues only offer best-effort, out-of-order delivery, so duplicate or late-arriving orders could be processed out of sequence.
Community Discussion (154 comments)
baromi8282
👍 1
Selected: B
b is correct, AWS SQS standard queue don't always ensure FIFO, so we need to use AWS sqs with FIFO protocol, then we can use Lambda for the processing.
suhan_14
👍 1
Selected: B
b is correct, AWS SQS standard queue don't always ensure FIFO, so we need to use AWS sqs with FIFO protocol, then we can use Lambda for the processing.
imvbhatia
👍 1
Selected: B
B is the correct answer because you need to maintain the sequence
suji098
👍 1
Selected: B
i think B is right answer because B letter is my favourite letter
suji098
👍 1
Selected: B
my self
Sukri123
👍 1
Selected: B
I think b is correct
Clouddon
👍 2
Selected: B
Use Amazon API Gateway → SQS FIFO Queue → Lambda to ensure ordered, reliable processing of incoming orders — meeting the ecommerce application's needs.
K_SAA
👍 1
Selected: B
keywords: orders should be process in the order when it receives B is correct answer, use API gateway intergation with FIFO SQS invoke lambda function for processing order A; SNS + lambda: SNS does not grant order messages to subscribers C: is not the correct one since we wanted to process the message in order so we do not have to block D: using standard queue does not grant the order of messages being sent
sdjfidhbgidfbivgv
👍 1
Selected: B
B SQS FIFO is made for that
offek
👍 1
Selected: B
FIFO make sure to send the data exactly in the same order
ak240519
👍 1
Selected: B
B is the only solution that guarantees message order.
adamatic
👍 1
Selected: B
Has to be FIFO queue for this requirement
Mrigraj12
👍 1
Selected: B
SQS FIFO as if want to maintain order of messages recieved to order of messages sent. It is like QUEUE data structutre in DSA
surez
👍 1
Selected: B
SQS FIFO gurantees message order.
MGKYAING
👍 3
Selected: B
Explanation: FIFO Queues: Amazon SQS FIFO queues are specifically designed to maintain the order of messages. This ensures that messages are processed in the exact sequence they were sent, which is crucial for order processing in an e-commerce application. Why other options are less suitable: A. Amazon SNS: SNS is a publish-subscribe service. It doesn't guarantee message order. C. API Gateway Authorizer: Authorizers are used for authentication and authorization, not for managing message order. D. Amazon SQS Standard Queue: Standard SQS queues do not guarantee message order.
ondan
👍 3
Standard queues ensure at-least-once message delivery, but due to the highly distributed architecture, more than one copy of a message might be delivered, and messages may occasionally arrive out of order.
Abishek016
👍 2
AnswerB - SQS FIFO queues ensure that messages are processed in the order they are received, which perfectly matches the requirement of maintaining order.
paobalinas
👍 2
A lot of answers seem to not match the most voted. i'm confused which to follow.
Sinaneos
👍 70
Selected: B
B because FIFO is made for that specific purpose
gx2222
👍 5
Selected: B
Explanation: To ensure that orders are processed in the order that they are received, the best solution is to use an Amazon SQS FIFO (First-In-First-Out) queue. This type of queue maintains the exact order in which messages are sent and received. In this case, the application can send information about new orders to an Amazon API Gateway REST API, which can then use an API Gateway integration to send a message to an Amazon SQS FIFO queue for processing. The queue can then be configured to invoke an AWS Lambda function to perform the necessary processing on each order. This ensures that orders are processed in the exact order in which they are received.
PhucVuu
👍 12
Selected: B
Keywords: - Orders are processed in the order that they are received. A: Incorrect - SNS just for notification like send email, SMS. It don't retain the data in the queue and it's used pub-sub pattern. B: Correct - SQS FIFO will help message process in order. FIFO -> first in first out. C: Incorrect - with this solution we will create blocker app not good app =)) D: Incorrect - SQS standard don't guarantee the order.
Guru4Cloud
👍 6
Selected: B
Explanation: - Amazon API Gateway will be used to receive the orders from the web application. - Instead of directly processing the orders, the API Gateway will integrate with an Amazon SQS FIFO queue. - FIFO (First-In-First-Out) queues in Amazon SQS ensure that messages are processed in the order they are received. - By using a FIFO queue, the order processing is guaranteed to be sequential, ensuring that the first order received is processed before the next one. - An AWS Lambda function can be configured to be triggered by the SQS FIFO queue, processing the orders as they arrive
Andreshere
👍 6
Selected: B
A. This option could be correct if we use SNS FIFO option, but this is not the case stated in the question. Additionally, this task is more efficient done by a queue than a subscription service. So, this option is not correct. B. We use a queue, which is efficient processing messages. Additionally, it preserves the order since it is a FIFO queue. Meanwhile we don’t have any kind of messages throughput limitation, this option is correct. C. This option discards any messages that are still processing, which is not a good solution. D. Same option as B but using a normal queue, which does not preserve the order. Incorrect.
PaulGa
👍 1
Selected: B
FIFO is crucial to ensuring the solution works. Two answers use SQS and the author has differentiated between these option by specifically stating in option B “FIFO” On the other hand, SNS also has a FIFO option but the author has chosen to not state that in answer A. If the author had said in option A: “…with FIFO” then A could have been a viable answer. Therefore it has to be Ans B (not A as the author recommends).
PaulGa
👍 1
FIFO is crucial to ensuring the solution works. Two answers (B & D) use SQS and the author has differentiated between these by specifically stating in answer B “FIFO”. On the other hand (answer A), SNS also has a FIFO option but the author has chosen to not state that in answer A. If the author had been consistent and said in answer A: “…with FIFO” then A could have been a viable answer. Therefore it has to be Ans B (not A as the author recommends).
pranavff_examtopics_1993
👍 1
Selected: B
FIFO ensures message order
aws_sungazer
👍 1
B. SQS FIFO as order of processing should be same as order of receiving
parth_g_mehta
👍 2
Selected: B
Use an Amazon SQS FIFO (First-In-First-Out) Queue to ensure that orders are processed in the exact order they are received. The FIFO queue guarantees message order and exactly-once processing.
ChymKuBoy
👍 1
Selected: B
B for sure
jaradat02
👍 3
Selected: B
what's up with all these strange answers!!!! I chose B, SQS FIFO is designed for this exact use case, why does the author claim that A is the correct answer??
OBIOHAnze
👍 1
Selected: B
B seems to be the answer
d675329
👍 2
Selected: B
I'll go ahead with B. But my grouse with Option B is it says "Configure the SQS FIFO queue". You configure the Lambda, not the SQS queue. The role for Lambda to access SQS is auto-configured by AWS.
Rabbit117
👍 2
Selected: B
I think B is the correct answer as SQS FIFO guarantees the order.
ManikRoy
👍 1
Selected: B
SQS FIFO Queue is for this use case.
hro
👍 3
B SNS - PubSub (think pass along) SQS - Queueing (think batch) Kinesis - Real-time SWF - Queuing but with people
JavierEF
👍 1
Selected: B
A is not correct becuase, if we do not specify that is an SNS FIFO, we have no guarantee the messages will be processed in publishing order.
Rosy92
👍 1
Selected: B
Orders have to be processed in order so SQS FIFO is requested here.
ldruizsan
👍 1
Selected: B
Although A is a viable option, the statement says it needs to ensure that messages are processed in the order they are received. That is FIFO by definition.
bigmancloud
👍 1
Amazon SQS FIFO Queue ensures that messages are processed in the order they are received
kioks23
👍 1
B - FIFO is designed for that
Sivadocker7
👍 1
Selected: B
B is correct
awsgeek75
👍 1
Selected: B
SQS FIFO is the only working solution here
A_jaa
👍 1
Selected: B
B is correct
awsgeek75
👍 1
B is the right answer because FIFO is a core requirement of the question.
cardebab
👍 2
Why it says is A when of course B is the right answer?
yonwick
👍 1
Selected: B
It's B, don't hesitate!
achechen
👍 1
Selected: B
B because of FIFO.
nathanss
👍 1
Selected: B
B again
ifaby
👍 1
Selected: A
It's A because the option B is wrong, SQS never invoke nothing, it's Lambda who reads the messages.
jors1116
👍 1
Selected: B
Keyword is FIFO
chry900
👍 1
Selected: B
b. SQS fifo
Ruffyit
👍 1
b. SQS fifo is made for first in first out
lorrangarcia
👍 1
Selected: B
B, devido ao uso do SQS
jasm33t
👍 1
Selected: B
in order = SQS FIFO
vishal08
👍 1
Selected: B
can any1 say what is right answer? and how its A?
bhavin042
👍 1
Selected: B
I think B is the correct answer, keyword FIFO to process orders in correct order.
avrk
👍 3
For most of the questions there is correct answer and votes given by group. Which one is the correct answer to consider as i am getting confused. who has given correct answer?
Zelda28
👍 1
Selected: B
Invoking lambda function is the right way, if we use standard, the orders would not be processed in the correct order. FIFO would give the correct order...
dbs6339
👍 1
I Was wrong answer B is correct
AWSGuru123
👍 1
Selected: B
FIFO queue suits best
praveenkumar2
👍 2
I vote for Option B, When the question says about order ......blindly go for SQS FIFO
dbs6339
👍 3
Selected: A
Answer is A, this is the order process. when ecommerce application an order topic occured. many consumer api subscribe this topic. so is it not proper using SQS. SNS using is the best.
dbs6339
👍 2
addtionally add more detail about the Rest api from question. the SQS FIFO is not proper option. because SQS is porpose one consumer. the rest api is consume many request so this case is correct that the SNS. SNS publish a topic that is fan out for many subscribers through some transfer methods. It's Could be SQS if after the SNS from the API gateway.
paobalinas
👍 1
How come answers do not match? I also think B is the correct answer coz of the FIFO mention
MakaylaLearns
👍 3
I made two short videos explaining why the answer is B Also we should note that sometimes SNS loses the message whilst SQS will hold onto the message until it can send it. These videos are super quick!
dwx101
👍 1
Nice one on the VID. I thought FIFO. I havee seen these sites before have the wrong answers. It is quite a few on this one though :( ...TY
benacert
👍 1
B it is..
chrisda
👍 1
option B
PLN6302
👍 1
option B
zjcorpuz
👍 1
B is the correct answer SQS configured as FIFO will suffice the requirement
prabhjot
👍 1
Ans is B(Amazon SQS FIFO queue.) - check the video here - https://aws.amazon.com/sqs/
james2033
👍 1
Selected: B
Keyword "orders are processed in the order that they are received", choose what has word "SQS", there are B and D. B is better than D, with keyword "FIFO" is exist.
Multiverse
👍 1
Selected: B
B. Process in the order received. SNS does not provide FIFO capabilities
jaydesai8
👍 1
Selected: B
B because FIFO is made for that specific purpose
animefan1
👍 1
B is correct. SQS fifo as order is important here
gustvomonteiro
👍 1
FIFO for sure, the correct is B
KAMERO
👍 1
Selected: B
First-in First-out strictly order
cookieMr
👍 5
Selected: B
Option B: Using an API Gateway integration to send a message to an Amazon SQS FIFO queue is the recommended solution. FIFO queues in Amazon SQS guarantee the order of message delivery, ensuring that orders are processed in the order they are received. By configuring the SQS FIFO queue to invoke an AWS Lambda function for processing, the application can process the orders sequentially while maintaining the order in which they were received.
karloscetina007
👍 1
Selected: B
B: because FIFO is made for that specific purpose. It's important takes in consideration that the orders must be processed in the order received.
Bmarodi
👍 1
Selected: B
Option B meets the requiremets.
HarryDinh209
👍 1
B is the correct answer, just remember FIFO for ordered messages
smash_aws
👍 1
sorry it cant be A. You gotta read the specs. You need Fifo. but sns fifo dont work without SQS FIFO configured. here is the docs view "To preserve strict message ordering, Amazon SNS restricts the set of supported delivery protocols for Amazon SNS FIFO topics. Currently, the endpoint protocol must be Amazon SQS, with an Amazon SQS FIFO queue's Amazon Resource Name (ARN) as the endpoint." also "To fan out messages from Amazon SNS FIFO topics to AWS Lambda functions, extra steps are required. First, subscribe Amazon SQS FIFO queues to the topic. Then configure the queues to trigger the functions" answer is B for the win
abhishek2021
👍 1
the most suitable item is B. However, , my understanding is that SQS can not invoke a lambda function. Lambda should be invoked by other means, maybe Eventbridge schedule or something else, and then it can check the poll message on queue. Experts request your confirmation.
smash_aws
👍 3
SQS queues sure can be configured to trigger functions
nishant_pruthi
👍 1
B is correct answer
redx1
👍 1
reponse : B
cheese929
👍 1
Selected: B
B is correct. processed in the order that they are received = SQS FIFO.
darkknight23
👍 6
Selected: B
I am new to this site and lost....Will appreciate if someone can explain why is "correct answer" shown in the solution always wrong?
dmt6263
👍 2
Read discussions mate
chibaniMed
👍 2
Selected: B
Amazon SNS FIFO Can only have SQS FIFO queues as subscribers which is not the case of answer C
owen0427
👍 2
Selected: B
B: Correct - SQS FIFO will help message process in order. FIFO -> first in first out.
Ankit_EC_ran
👍 2
Selected: B
SQS FIFO will help the message process in order.
channn
👍 1
Selected: B
Key words: in the order = SQS
Dinya_jui
👍 1
answer is B, because FIFO is made for guaranteed message order
acuaws
👍 1
Selected: B
When you see the phrase "in order" you automatically go for SQS.
lawren
👍 2
Not always the case cause standard queues can be delivered not in order
Branco1
👍 1
Selected: B
Acho que é a B
kraken21
👍 1
Selected: B
B FIFO
AnweshaRoy
👍 1
B because SQS is more suitable for message cases
arakokeba
👍 2
B because we need to process as FIFO. I don't rely on SNS for ordering, and it's prone to errors.
PaoloRoma
👍 1
Selected: B
A) SNS doesn't guarantee ordering. This might work with low number of orders, but this is not ready to scale B) SQS FIFO queue is deisgned to preserve message ordering C) blocking request while app process order makes the app synchronous and it limit scalability D) SQS standard queue doesn't guarantee message ordering (best effort)
tienhoboss
👍 1
Selected: B
B is correct
volkan4242
👍 1
B Because of FIFO
saransh_001
👍 1
Selected: B
B should be correct FIFO is needed
jaswantn
👍 1
Company is building application , so this is not overloaded with the order(nowhere mentioned in the question). If orders are generated in sequence and notification is sent to SNS, then order would remain intact. Using SQS(FIFO) would bring more cost( which we need to avoid always).
sanking
👍 1
Selected: A
SQS is distributed queueing system. Messages are sent into a queue and receivers have to poll messages from SQS. How let Restful API poll? SNS messages are pushed to subscribers. So I select A - SNS.
mark543
👍 1
Selected: B
Only FIFO can meet the demand
To_mi
👍 5
Who decides what option is marked as a correct answer? Most of them are incorrect. The correct answer to this question is B.
KittieHearts
👍 1
Selected: B
It's B FIFO
bilel500
👍 1
Selected: B
Standard queues provide best-effort ordering which ensures that messages are generally delivered in the same order as they are sent. Occasionally (because of the highly-distributed architecture that allows high throughput), more than one copy of a message might be delivered out of order. FIFO queues offer first-in-first-out delivery and exactly-once processing: the order in which messages are sent and received is strictly preserved.
rhm
👍 1
Selected: B
Should be B
khasport
👍 1
almost people choice B and me too. But I don't know why correct answer is A and who is make correct answer ? is it admin of examtopic page ?
buiducvu
👍 2
Selected: B
Amazon Simple Queue Service (Amazon SQS) FIFO
MoMoCh4n
👍 8
Selected: B
I think the wrong answers are here intentionally as a way for us to deep dive into the topic and gain more knowledge or maybe I'm giving them too much credit.
Andrew123123
👍 1
Highly doubt it. There is app with identical questions and wrong answers named TestKing that gives you the wrong answers too with no feedback from people or explanations of answers.
goodmail
👍 3
Answer is B SNS has FIFO topics for ordering and deduplication, but the answer does not mention that. So answer A can be assumed to be standard one without ordering feature.
dexpos
👍 3
Hi folks, I just asked to the support about having different suggested answer vs the one selected from the community and the reply is: "If the provided answer is not correct or against the discussion then you can go with the user voted ones." . Community wins if we agree :). Hope this helps.
Ello2023
👍 1
Answer B. API Gateway endpoint sits in between applications and integration. It works like a tunnel which connects to SQS service. Once the connection is established you have two services Standard SQS which transmits without order and is scaleable and FIFO Queue where everything is sent in the same order.
Buruguduystunstugudunstuy
👍 3
Selected: B
CORRECT ANSWER Option B, using an API Gateway integration to send a message to an Amazon Simple Queue Service (SQS) FIFO queue when the application receives an order and configuring the SQS FIFO queue to invoke an AWS Lambda function for processing, would meet the requirements specified in the prompt. SQS FIFO queues ensure that messages are processed in the order that they are received, and API Gateway integrations allow you to send messages to an SQS queue when certain events occur, such as when the application receives an order. By configuring the SQS FIFO queue to invoke an AWS Lambda function for processing, you can ensure that orders are processed in the order that they are received.
Buruguduystunstugudunstuy
👍 1
INCORRECT ANSWERS Option A, using an API Gateway integration to publish a message to an Amazon Simple Notification Service (SNS) topic and subscribing an AWS Lambda function to the topic, would not guarantee that orders are processed in the order that they are received. Option C, using an API Gateway authorizer to block requests while the application processes an order, would not allow for parallel processing of orders and could lead to delays in processing. Option D, using an API Gateway integration to send a message to an SQS standard queue, would not guarantee that orders are processed in the order that they are received.
Zerotn3
👍 1
why Correct Answer is A ? it's answer offical
wacze
👍 2
Answer is A because SNS is typically used for applications that need real time notifications. considering this (The application sends information about new orders to an Amazon API Gateway REST API to process")
BENICE
👍 1
B is correct answer
lrraju
👍 7
All - please help. I am taking this test, but my answers mostly align with most voted. What's the right answer? Should we go with the most voted as correct answer or what the website suggests as the correct answer?
Lonojack
👍 2
I think the highlighted answers are to throw off the Bots or people trying to copy the admins materials and Sell it on another platform. That’s the only thing that makes logical sense to me. Btw, Correct answer is obviously (B) 😉
LuckyAro
👍 4
I would go with most voted because there have been times when the Admin's answered have been blatantly wrong and makes me question Admin's handle of the subject matter. 100% of us can't be wrong simultaneously.
Zerotn3
👍 3
same my confusing :(
rajesh1216
👍 1
Selected: B
I go with B
NikaCZ
👍 2
Selected: B
The answer is B.
yoben84
👍 1
can someone explain why it is A? we can't be all wrong
rajesh1216
👍 1
It should be: B FIFO Queue maintains the sequencing
Nandan747
👍 3
Selected: B
I don't understand why ALMOST EVERY QUESTION has a wrong answer highlighted. Clearly something is NOT right. And the answer is B, because requirement clearly states order to be followed and SQS FIFO ensures that.
rvenkatpsg
👍 1
Selected: B
FIFO is correct one
AlaN652
👍 1
Selected: B
Answer is B. the SQS FIFO queue should be used in this scenario
ogwu2000
👍 1
A. Can API Gateway integration sends a message or publishes a message?
Drekorig
👍 2
Selected: B
Answers A, B and D are possible, but to guarantee the order of the messages the answer is B
leonnnn
👍 1
Selected: B
SQS FIFO queue guraantees message order.
akellaaws
👍 1
Selected: B
SQS FIFO can be an event source for Lambda
raqsa
👍 1
Selected: B
yes B is correct
Buruguduystunstugudunstuy
👍 1
KEYWORDS: "processed in the order that they are received" FIFO, First·In·First·Out The answer is B. Amazon SQS FIFO
emyhe
👍 1
should be B, because require message order, FIFO have First-in-First-Out Delivery feature.
Paritoshjani
👍 2
SQS is not a push service. Hence the consumer has to poll. SQS FIFO queue cannot invoke Lambda; it is reverse. While SNS can publish record to Lambda. Hence the more appropriate answer is A
Hasu_Uchiha
👍 2
AWS Lambda now supports Amazon SQS First-In-First-Out (FIFO) as an event source.
keezbadger
👍 1
The right answer is B
Six_Fingered_Jose
👍 1
Selected: B
answer is B here > ensure that orders are processed in the order that they are received. only SQS with FIFO here meets that condition
PhilN135
👍 1
B - FIFO
alvarez100
👍 2
B FIFO !
arthurfl
👍 2
Selected: B
FIFO works here, son the answer is B
BoboChow
👍 2
Selected: B
SQS FIFO queue works for the secario
sba21
👍 2
Selected: B
FIFO is made for that
hanhdroid
👍 2
Selected: B
B to guarantee message order
pooppants
👍 2
Selected: B
FIFO support
tuloveu
👍 8
Selected: B
To processed in the order that they are received.
rein_chau
👍 28
Selected: B
Should be B because SQS FIFO queue guarantees message order.
Comments & Corrections
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Expert Analysis
Why the Answer Is Correct
Option B sends each new order through an API Gateway integration into an Amazon SQS FIFO queue, which guarantees strict first-in, first-out ordering of messages, and the queue is configured to trigger an AWS Lambda function for processing. FIFO queues support message grouping and ordering, exactly matching the requirement that orders be processed in the order they are received. The queue also decouples intake from processing, providing buffering and retries without blocking the API. This design satisfies the ordering requirement while remaining loosely coupled and scalable.Why the Other Options Are Wrong
Option A uses a standard Amazon SNS topic, a pub/sub notification service that neither stores messages durably for ordered replay nor guarantees delivery order to subscribers. Option C blocks all requests through an API Gateway authorizer while processing, which serializes the whole API and destroys availability — it neither preserves queue order nor is a sensible architecture. Option D uses an SQS standard queue, which offers high throughput but only best-effort ordering, so messages can be delivered out of order and the stated requirement is not met. As PhucVuu explained, SNS is a notification/pub-sub mechanism that does not retain data in a queue, while the SQS standard queue simply lacks ordering guarantees.Community Comment Notes
The community converged overwhelmingly on B, with Sinaneos noting "B because FIFO is made for that specific purpose" and rein_chau adding that an "SQS FIFO queue guarantees message order." Guru4Cloud walked through why API Gateway should integrate with the FIFO queue so processing is "guaranteed to be sequential." Andreshere pointed out that even an SNS FIFO option was not what the question described, and that a queue suits this task better than a subscription service. Two commenters, lrraju and darkknight23, asked whether the site's displayed answer could be trusted over the vote majority; here the vote majority and the AWS ordering semantics both point to B.Official Reference
Exam Strategy
When a question demands strict ordering, latency sequencing, or exactly-once processing, scan the options for SQS FIFO — it is the standard AWS answer. Dismiss SNS and standard SQS immediately, since neither guarantees order.
Frequently Asked Questions
Why is an SQS standard queue wrong when it can also trigger Lambda?
Standard queues provide high throughput but only best-effort ordering, so messages may be processed out of sequence. The requirement here is strict arrival-order processing, which only a FIFO queue satisfies.
Why can't an SNS topic preserve order for these orders?
SNS is a pub/sub notification service that fans out messages to subscribers without durable, ordered queuing. A standard SNS topic has no ordering guarantee, so a FIFO queue is required.
Related Analysis
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