AWS Data Engineering Fundamentals

A database table contains rows and columns with a predefined schema. What type of data is this?

Structured

Which is the BEST example of semi-structured data?

JSON document

Which is MOST likely unstructured data?

Video recording

A company stores several petabytes of customer transaction records. Which characteristic of data does this primarily describe?

Volume

An IoT platform receives sensor readings every millisecond and must process them immediately. Which characteristic is MOST relevant?

Velocity

A company combines SQL tables, JSON logs, emails, images, and customer reviews. Which characteristic is MOST relevant?

Variety

Which characteristic BEST describes a data warehouse?

Primarily stores structured, transformed data for analytical queries

Which characteristic BEST describes a data lake?

Stores large amounts of raw data in its native format

A company has structured sales data and needs fast, complex BI queries. Which should it favor?

Data warehouse

A company has JSON logs, images, videos, CSV files, and future analytical requirements that are not yet known. Which is MOST appropriate?

Data lake

Which statement correctly compares schema-on-write and schema-on-read?

Warehouses commonly use schema-on-write; data lakes commonly use schema-on-read.

What is the primary idea behind a data lakehouse?

Combine data lake flexibility with data warehouse capabilities

A company organizes data ownership around business domains. Each domain team owns its own data products while central standards provide governance. What concept does this describe?

Data mesh

Which sequence correctly describes ETL?

Extract → Transform → Load

Which activity belongs in the Extract stage?

Retrieving data from an API

Which is an example of transformation?

Removing duplicate records

A pipeline converts dates from MM/DD/YYYY to ISO format, removes duplicates, and calculates total sales. Which ETL phase is responsible?

Transform

Which can occur during the Load stage?

Moving transformed data into the target repository

A company needs its ETL workflows to execute automatically, reliably, and in the proper order. What capability is MOST relevant?

Orchestration

Which technology provides a standardized interface for connecting applications to relational databases?

JDBC

Which is a common data source for a data pipeline?

All of the above

Which format is text-based, tabular, and commonly uses commas to separate values?

CSV

Which format is particularly appropriate when you need flexible, nested key-value data?

JSON

Which format stores both data and its schema and is useful for schema evolution?

Avro

A data engineer wants an analytical file format that efficiently reads only the columns required by a query. Which should they favor?

Parquet

An analytics engine needs only three columns from a dataset containing 100 columns. Which format would generally be MOST efficient?

Parquet

A data warehouse contains a central sales table connected to customer, product, and date tables. What modeling approach is this?

Star Schema

In a typical star schema, what does a fact table primarily contain?

Measures/events and keys linking to dimensions

Which objects commonly appear in an entity relationship diagram?

Primary keys and foreign keys

What does data lineage describe?

The flow and transformation of data from source to destination

A report contains an incorrect value. The data engineer wants to determine which upstream transformation introduced the error. What capability is MOST useful?

Data lineage

A source application adds a new column to its dataset without breaking existing consumers. What concept describes the ability of systems to adapt to this change?

Schema evolution

Why is schema evolution important?

It allows datasets to change over time without unnecessarily breaking downstream systems.

Which technique can reduce the amount of data scanned by a query?

Partitioning

What is one major benefit of compression?

It reduces storage and can reduce data transfer/I/O.

A distributed processing job is slow because one partition contains dramatically more records than the others. What problem is occurring?

Data skew

Which technique can help address a highly skewed partition key?

Salting

A data engineer randomly selects records so that every record has an equal probability of selection. Which sampling technique is this?

Random sampling

A dataset contains customers from four geographic regions. The engineer wants each region represented in the sample. Which technique is BEST?

Stratified sampling

A dataset contains 10,000 records, but 2,000 are missing required customer IDs. Which quality dimension is affected?

Completeness

A customer’s address differs between two trusted source systems. Which quality dimension is MOST directly involved?

Consistency

A customer’s recorded age is -15. Which issue is MOST directly involved?

Accuracy/validity

A foreign key references a customer that does not exist in the customer table. Which quality concept is MOST directly violated?

Referential Integrity

A data engineer wants to determine whether required fields contain NULL values and whether IDs are unique. What activity should be performed?

Data profiling/validation

Which SQL function counts rows?

Count()

Which function calculates the average value of a numeric column?

Avg()

A data engineer needs to calculate the number of employees earning more than $70,000. Which approach is appropriate?

COUNT(CASE WHEN salary > 70000 THEN 1 END)

Which SQL operation combines rows from two tables based on related columns?

JOIN

You need every customer from the customer table, even if the customer has no matching order. Which join is MOST appropriate?

Left Outer Join

A query needs to match rows where a string begins with either “fire” or “ice” using a regular expression. Which concept is being used?

Regex pattern matching

Which Git command creates a new repository?

git init

Which command stages changes for a commit?

git add

Which command creates a new branch and switches to it?

git checkout -b

Which Git command creates a new commit that reverses the changes introduced by a previous commit?

git revert

A developer wants to temporarily save uncommitted changes and return to a clean working tree. Which command should they use?

git stash

A developer accidentally loses a commit and wants to inspect previous reference movements to recover it. Which Git feature is useful?

git reflog