A developer is designing a real-time inventory management microservice that uses an Amazon… — AWS Certified Developer - Associate

A developer is designing a real-time inventory management microservice that uses an Amazon DynamoDB table. The application needs to support the following operations during peak traffic:

* $10$ `TransactWriteItems` operations per second. Each transaction contains two write actions: one writes a new item of $3.5\text{ KB}$ , and another updates an existing item resulting in a final size of $1.5\text{ KB}$ .
* $15$ standard `PutItem` operations per second, with an average item size of $4.5\text{ KB}$ .
* $40$ `TransactGetItems` operations per second. Each transaction reads a single item of $6\text{ KB}$ .

To ensure optimal performance, scalability, and security under the AWS shared responsibility model, which capacity provisioning and development strategy should the developer implement?

Provision $195$ Write Capacity Units (WCUs) and $160$ Read Capacity Units (RCUs). Configure the application to use the default credential provider chain and retrieve items using Query or TransactGetItems operations instead of Scan.Answer
B
Provision $135$ Write Capacity Units (WCUs) and $80$ Read Capacity Units (RCUs). Retrieve items using TransactGetItems operations, and initialize the DynamoDB client by passing hardcoded IAM access keys directly into the SDK constructor.
C
Provision $195$ Write Capacity Units (WCUs) and $480$ Read Capacity Units (RCUs). To prevent partition hotness and optimize downstream processing, replace single-item query operations with parallel Scan operations that periodically read the entire table.
D
Provision $168$ Write Capacity Units (WCUs) and $160$ Read Capacity Units (RCUs). If the application encounters a ProvisionedThroughputExceededException, immediately configure DynamoDB Auto Scaling to scale up provisioned capacity to resolve the error.

Answer

Provision

195

Write Capacity Units (WCUs) and

160

Read Capacity Units (RCUs). Configure the application to use the default credential provider chain and retrieve items using Query or TransactGetItems operations instead of Scan.

The correct strategy provisions

195

WCUs and

160

RCUs, uses the default credential provider chain for secure authentication, and retrieves specific items efficiently via Query or TransactGetItems instead of Scan. The Write Capacity Unit (WCU) calculation is as follows: The TransactWriteItems workload consists of

10

operations/second. Each operation has two write actions: a new item of

3.5\text{ KB}

(rounded up to

4\text{ KB}

, costing

4\text{ WCUs} \times 2

for transactional writes =

8\text{ WCUs}

) and an update resulting in a

1.5\text{ KB}

item (rounded up to

2\text{ KB}

, costing

2\text{ WCUs} \times 2

for transactional writes =

4\text{ WCUs}

). This totals

12\text{ WCUs}

per transaction, or

120\text{ WCUs}

for

10

transactions/second. The standard PutItem workload consists of

15

operations/second of

4.5\text{ KB}

(rounded up to

5\text{ KB}

, costing

5\text{ WCUs}

). This consumes

75\text{ WCUs}

. Summing these values gives

195\text{ WCUs}

. The Read Capacity Unit (RCU) calculation is as follows: The TransactGetItems workload consists of

40

operations/second. Each transaction reads one

6\text{ KB}

item (rounded up to the nearest

4\text{ KB}

boundary, which is

8\text{ KB}

, consuming

2\text{ RCUs}

). Since transactional reads consume double the RCUs of strongly consistent reads, each transaction costs

4\text{ RCUs}

, totaling

160\text{ RCUs}

for

40

operations/second.

Step-by-Step Solution

Calculate the Write Capacity Units (WCUs) required for the

10

TransactWriteItems operations per second.

120

WCUs

Each transaction contains two write actions. Action 1 (

3.5\text{ KB}

) is rounded up to

4\text{ KB}

and multiplied by

2

for transaction writes, yielding

8\text{ WCUs}

. Action 2 (

1.5\text{ KB}

) is rounded up to

2\text{ KB}

and multiplied by

2

, yielding

4\text{ WCUs}

. Total per transaction is

12\text{ WCUs}

. For

10\text{ operations/sec}

, this consumes

10 \times 12 = 120\text{ WCUs}

Calculate the WCUs required for the

15

standard PutItem operations per second.

75

WCUs

Each standard write of

4.5\text{ KB}

is rounded up to

5\text{ KB}

and consumes

5\text{ WCUs}

. For

15\text{ operations/sec}

, this consumes

15 \times 5 = 75\text{ WCUs}

Sum the WCU requirements to find the total provisioned WCU.

195

WCUs

Combining the transactional writes (

120\text{ WCUs}

) and standard writes (

75\text{ WCUs}

) yields a total required write capacity of

195\text{ WCUs}

Calculate the Read Capacity Units (RCUs) required for the

40

TransactGetItems operations per second.

160

RCUs

Transactional reads are strongly consistent and consume double the capacity of standard strongly consistent reads. Reading a

6\text{ KB}

item requires rounding up to the nearest

4\text{ KB}

boundary (

8\text{ KB}

), consuming

2\text{ RCUs}

for a standard strongly consistent read. Doubling this for the transaction results in

4\text{ RCUs}

per operation. For

40\text{ operations/sec}

, this consumes

40 \times 4 = 160\text{ RCUs}

Evaluate the architectural and security configurations.

Use the default credential provider chain and query/retrieve items directly rather than scanning.

Hardcoding credentials violates security best practices, and using Scan operations instead of Query or specific read APIs is highly inefficient and consumes excess RCUs.

Key Concept

DynamoDB capacity calculation for transactional and standard operations combined with security and query optimization

Estimated Time:3m 0s

Question

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Step-by-Step Solution

Key Concept

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