S90-09A · Question #14
Service A is an entity service that provides a set of generic and reusable service capabilities. In order to carry out the functionality of any one of its service capabilities, Service A is required…
The correct answer is C. The Redundant Implementation pattern can be applied to Service B, thereby making duplicate. Option C is correct because applying the Redundant Implementation pattern to Service B directly targets the root cause of the cascading failure: when Service B goes down, Service A goes down with it. By deploying multiple redundant instances of Service B, the service inventory…
Question
Service A is an entity service that provides a set of generic and reusable service capabilities. In order to carry out the functionality of any one of its service capabilities, Service A is required to compose Service B (1) and Service C (2) and Service A is required to access Database A (3), Database B (4), and Database C (5). These three databases are shared by other applications within the IT enterprise. All of service capabilities provided by Service A are synchronous, which means that for each request a service consumer makes. Service A is required to issue a response message after all of the processing has completed. Depending on the nature of the service consumer request, Service A may be required to hold data it receives in memory until its underlying processing completes. This includes data it may receive from either Service A or Service B or from any of the three shared databases. Service A is one of many entity services that reside in a highly normalized service inventory. Because Service A provides agnostic logic, it is heavily reused and is currently part of many service compositions. You are told that Service A has recently become unstable and unreliable. The problem has been traced to two issues with the current service architecture. First, Service B, which is also an entity service, is being increasingly reused and has itself become unstable and unreliable. When Service B fails, the failure is carried over to Service A . Secondly, shared Database B has a complex data model. Some of the queries issued by Service A to shared Database B can take a very long time to complete. What steps can be taken to solve these problems without compromising the normalization of the service inventory?
Exhibit
Options
- AThe Redundant Implementation pattern can be applied to Service A, thereby making duplicate
- BThe Redundant Implementation pattern can be applied to Service B, thereby making duplicate
- CThe Redundant Implementation pattern can be applied to Service B, thereby making duplicate
- DNone of the above.
How the community answered
(26 responses)- A31% (8)
- B8% (2)
- C50% (13)
- D12% (3)
Explanation
Option C is correct because applying the Redundant Implementation pattern to Service B directly targets the root cause of the cascading failure: when Service B goes down, Service A goes down with it. By deploying multiple redundant instances of Service B, the service inventory gains failover capability, so Service A can route requests to a healthy instance without service interruption, and normalization is preserved because no new service boundaries are being created-just duplicated deployment units.
Option A is wrong because applying Redundant Implementation to Service A treats the symptom (Service A's unreliability) rather than the cause; Service A would still call an unstable Service B, so redundant copies of Service A would all fail in tandem. Option B likely describes an incomplete or incorrect application of the pattern-for example, addressing only one of the two problems (Database B's slow queries) through redundancy alone, which does not resolve the underlying query performance issue and is not the right pattern for that problem.
Memory tip: Think "fix the source, not the symptom." Redundant Implementation belongs on the failing dependency (Service B), not on the consumer (Service A) that's suffering because of it. If a power outlet is broken, you replace the outlet-not every device plugged into it.
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