Master the MuleSoft Certified Integration Architect - Level 1 MAINTENANCE MCIA-Level-1-Maintenance Exam with Confidence!

Explanation

Before we answer this question , we need to understand what median (50th percentile) and 80th percentile means. If the 50th percentile (median) of a response time is 500ms that means that 50% of my transactions are either as fast or faster than 500ms.

If the 90th percentile of the same transaction is at 1000ms it means that 90% are as fast or faster and only 10% are slower. Now as per upstream SLA , 99th percentile is 800 ms which means 99% of the incoming requests should have response time less than or equal to 800 ms. But as per one of the backend API , their 95th percentile is 1000 ms which means that backend API will take 1000 ms or less than that for 95% of. requests. As there are three API invocation from upstream API , we can not conclude a timeout that can be set to meet the desired SLA as backend SLA's do not support it.

Let see why other answers are not correct.

1) Do not set a timeout --> This can potentially violate SLA's of upstream API

2) Set a timeout of 100 ms; ---> This will not work as backend API has 100 ms as median meaning only 50% requests will be answered in this time and we will get timeout for 50% of the requests. Important thing to note here is, All APIs need to be executed sequentially, so if you get timeout in first API, there is no use of going to second and third API. As a service provider you wouldn't want to keep 50% of your consumers dissatisfied. So not the best option to go with.

*To quote an example: Let's assume you have built an API to update customer contact details.

- First API is fetching customer number based on login credentials

- Second API is fetching Info in 1 table and returning unique key

- Third API, using unique key provided in second API as primary key, updating remaining details

* Now consider, if API times out in first API and can't fetch customer number, in this case, it's useless to call API 2 and 3 and that is why question mentions specifically that all APIs need to be executed sequentially.

3) Set a timeout of 50 ms --> Again not possible due to the same reason as above Hence correct answer is No timeout is possible to meet the upstream API's desired SLA; a different SLA must be negotiated with the first downstream API or invoke an alternative API

Explanation

* Resilience testing is a type of software testing that observes how applications act under stress. It's meant to ensure the product's ability to perform in chaotic conditions without a loss of core functions or data; it ensures a quick recovery after unforeseen, uncontrollable events.

* In case an API invocation fails — even after a certain number of retries — it might be adequate to invoke a different API as a fallback. A fallback API, by definition, will never be ideal for the purpose of the API client, otherwise it would be the primary API.

* Here are some examples for fallback APIs:

- An old, deprecated version of the same API.

- An alternative endpoint of the same API and version (e.g. API in another CloudHub region).

- An API doing more than required, and therefore not as performant as the primary API.

- An API doing less than required and therefore forcing the API Client to offer a degraded service, which is still better than no service at all.

* API clients implemented as Mule applications offer the ‘Until Successful Scope and Exception’ strategies at their disposal, which together allow configuring fallback actions such as a fallback API invocation.

* All HTTP response status codes within the 3xx category are considered redirection messages. These codes indicate to the user agent (i.e. your web browser) that an additional action is required in order to complete the request and access the desired resource

Diagram Description automatically generated

Hence correct answer is Redirect client requests through an HTTP 303 temporary redirect status code to the fallback API whenever the Order API is unavailable

Explanation

The API consumer creates an API client which sends API invocations to an API such that they are processed by an API implementation

This is based on below definitions API client • An application component • that accesses a service • by invoking an API of that service - by definition of the term API over HTTP API consumer • A business role, which is often assigned to an individual • that develops API clients, i.e., performs the activities necessary for enabling an API client to invoke APIs API implementation • An application component • that implements the functionality