Exam DP-900 topic 1 question 129 discussion

Column-family database is the low latency store type. Examples • Recommendations • Personalization • Sensor data • Telemetry • Messaging • Social media analytics • Web analytics • Activity monitoring • Weather and other time-series data

Answer may be A. Key/Value stores have fast response time, i.e. low latency. Columnar is good for Analytical. Here question is for Low Latency of a Web User's session data. Not analytical.

lowest latency

As per Microsoft , examples of using key/value are Data caching Session management -> mentioned clearly in question User preference and profile management Product recommendation and ad serving

option C

why not document ? D. document Document stores provide a good balance of flexibility and performance for scenarios where the data is semi-structured or has varying attributes, making them well-suited for managing session data with low-latency retrieval requirements.

"Most column-family databases perform write operations extremely quickly." from https://learn.microsoft.com/en-us/azure/architecture/guide/technology-choices/data-store-overview

Key/value data stores are optimized for simple lookups based on a unique key. In this case, the session data can be stored and retrieved using unique keys, such as session IDs. Key/value data stores offer fast retrieval times as they directly map the keys to the corresponding values without the need for complex querying or indexing.

response from CHATGPT: In this scenario, a key/value data store would likely provide the lowest latency to retrieve the data. Key/value stores are optimized for fast data access and retrieval, and they are ideal for use cases where data is frequently read and written in a simple key-value format. Session data for a website typically involves frequent reads and writes of small amounts of data. Notifications, personalization attributes, and products in a shopping cart can be stored as simple key-value pairs. Therefore, a key/value data store would be a good choice for achieving low latency. On the other hand, columnar data stores are optimized for querying and analyzing large datasets. They are ideal for use cases where data is frequently analyzed, aggregated, or transformed. In this scenario, since the data is not likely to be analyzed or transformed at scale, a columnar data store may not be the best choice for achieving low latency.

Key/value databases hold a single serialized object for each key value. They're good for storing large volumes of data where you want to get one item for a given key value and you don't have to query based on other properties of the item. Column-family databases are key/value data stores that structure data storage into collections of related columns called column families. For example, a census database might have one group of columns for a person's name (first, middle, last), one group for the person's address, and one group for the person's profile information (data of birth, gender). The database can store each column family in a separate partition, while keeping all of the data for one person related to the same key. An application can read a single column family without reading through all of the data for an entity.

It seems to me that the question is about which datastore will provide the lowest latency to retrieve the data, not which storage is best for the application. Column-family databases will do that job. https://learn.microsoft.com/en-us/azure/architecture/guide/technology-choices/data-store-overview

Per my understanding, columnar is the right answer Workload - Designed to provide high throughput and low-latency access. Examples - Recommendations, Personalization,Activity monitoring, etc https://learn.microsoft.com/en-us/azure/architecture/guide/technology-choices/data-store-overview

https://learn.microsoft.com/en-us/azure/architecture/guide/technology-choices/data-store-overview

I use my intuition.

In the URL cited by many people, the name Columnar no longer exists

key/value is good for fast lookups which the requested data mainly is; and asking for fast retrieval, updates not mentioned

Answer C: the content of a shopping cart can be changed. The key/value storage cannot be updated.