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NCEA Level 3 Digital Technologies study materials
NCEA Level 3 Digital Technologies study resources

NCEA Level 3 Digital Technologies practice questions

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Question 1Digital Technologies (content domains not enumerated in source)

In a relational database, which key uniquely identifies each record in a table and cannot contain null values?

  1. Composite key
  2. Primary key Correct answer.
  3. Candidate key
  4. Foreign key

Explanation

A primary key is the column or set of columns chosen to uniquely identify every row, and by definition it must be unique and non-null. Foreign keys reference other tables, candidate keys are possible identifiers not yet chosen, and composite keys use multiple columns but are not automatically the primary identifier.

Question 2Digital Technologies (content domains not enumerated in source)

A development team wants to merge code changes frequently while automating testing on each merge. Which practice directly supports this goal?

  1. Big-bang deployment
  2. Continuous integration Correct answer.
  3. Manual regression testing
  4. Waterfall scheduling

Explanation

Continuous integration means developers merge small changes often into a shared branch, with automated builds and tests running on each merge to catch defects early. Manual regression testing, waterfall scheduling, and big-bang deployment all delay feedback rather than automate it per merge.

Question 3Digital Technologies (content domains not enumerated in source)

Which protocol is used by a web browser to request and receive web pages over an encrypted connection?

  1. DHCP
  2. SMTP
  3. HTTPS Correct answer.
  4. FTP

Explanation

HTTPS carries HTTP traffic inside a TLS session, providing encryption and server authentication for web page requests. FTP transfers files, SMTP sends email, and DHCP assigns network configuration such as IP addresses.

Question 4Digital Technologies (content domains not enumerated in source)

A student writes pseudocode that loops while a counter is less than 5, adding 1 to the counter each iteration. How many times does the loop body execute if the counter starts at 0?

  1. 5 Correct answer.
  2. 1
  3. 4
  4. 6

Explanation

The condition counter < 5 is true for 0, 1, 2, 3, and 4, giving five iterations before the counter reaches 5 and the loop stops. Off-by-one errors are common when the starting value or the comparison operator is misread.

Question 5Digital Technologies (content domains not enumerated in source)

Which data structure follows a last-in, first-out order?

  1. Linked list
  2. Queue
  3. Stack Correct answer.
  4. Array

Explanation

A stack removes the most recently added item first, so its ordering is last-in, first-out. A queue is first-in, first-out, while arrays and linked lists are general collections whose access order depends on how they are used.

Question 6Digital Technologies (content domains not enumerated in source)

What is the main purpose of version control software such as Git in a digital project?

  1. Managing server memory allocation
  2. Compiling source code into executables
  3. Tracking changes to files and enabling collaboration Correct answer.
  4. Encrypting files on the developer's disk

Explanation

Version control records a history of changes to files, lets developers compare and revert revisions, and supports collaboration through branches and merges. Compilation, disk encryption, and memory management are handled by other tools.

Question 7Digital Technologies (content domains not enumerated in source)

Which statement best describes a phishing attack?

  1. A program floods a server with traffic until it fails
  2. A deceptive message tricks a user into revealing credentials Correct answer.
  3. A weakness in software is exploited before a patch exists
  4. A file is encrypted and held for ransom

Explanation

Phishing uses fraudulent messages, often mimicking trusted organisations, to persuade users to hand over passwords or other sensitive data. Flooding a server describes a denial-of-service attack, encryption for ransom describes ransomware, and exploiting an unpatched flaw describes a zero-day attack.

Question 8Digital Technologies (content domains not enumerated in source)

In the design of a digital outcome, what does the term 'usability' refer to?

  1. How quickly the source code compiles
  2. How much storage the product consumes
  3. How effectively users can achieve their goals with the product Correct answer.
  4. How many features the product includes

Explanation

Usability concerns how effectively, efficiently, and satisfactorily a specified set of users can achieve their goals in a particular context of use. Compilation speed, storage use, and feature count are technical or quantitative measures rather than usability.

Question 9Digital Technologies (content domains not enumerated in source)

A database table stores customer orders. To avoid repeating the full customer name and address on every order row, the designer splits customers into a separate table linked by a customer ID. Which concept does this illustrate?

  1. Denormalisation
  2. Indexing
  3. Sharding
  4. Normalisation Correct answer.

Explanation

Normalisation organises data into related tables to reduce redundancy and update anomalies, so customer details are stored once and referenced by an identifier. Denormalisation deliberately reintroduces redundancy, indexing speeds lookups, and sharding distributes data across servers.

Question 10Digital Technologies (content domains not enumerated in source)

A function is meant to return the largest value in a list. For the list [3, 8, 2, 8, 5] it returns 8. Which statement about this result is accurate?

  1. It is correct only if the list is sorted first
  2. It is correct because 8 is the maximum value present Correct answer.
  3. It is incorrect because the list contains duplicates
  4. It is incorrect because the function should return the index

Explanation

The maximum value in the list is 8, and duplicates do not change the maximum, so the function has produced the expected result. Sorting is not a prerequisite for finding a maximum, and returning an index would be a different specification.

Question 11Digital Technologies (content domains not enumerated in source)

Which change would most improve the accessibility of a website for users who rely on screen readers?

  1. Adding descriptive alternative text to meaningful images Correct answer.
  2. Placing all navigation inside a single image map
  3. Increasing the number of animated banners
  4. Using images of text instead of real text

Explanation

Screen readers announce alternative text for images, so meaningful images need descriptive alt attributes to convey their content. Animated banners can distract, text-as-image cannot be read or resized, and image maps are poorly conveyed to assistive technology.

Question 12Digital Technologies (content domains not enumerated in source)

A web application receives a user's name in a search form and inserts it directly into a SQL query. Which vulnerability does this create?

  1. Buffer overflow
  2. SQL injection Correct answer.
  3. Cross-site scripting
  4. Session fixation

Explanation

Concatenating untrusted input directly into SQL allows an attacker to alter the query structure, which is SQL injection. Cross-site scripting targets the browser output, buffer overflow involves memory bounds, and session fixation concerns session identifiers.

Question 13Digital Technologies (content domains not enumerated in source)

A team uses a sprint of two weeks with daily stand-ups and a product backlog. Which development approach does this describe?

  1. V-model
  2. Waterfall
  3. Agile Scrum Correct answer.
  4. Spiral model

Explanation

Short time-boxed sprints, daily stand-ups, and a prioritised backlog are core Scrum practices within agile development. Waterfall and the V-model are sequential, and the spiral model is risk-driven with iterative prototyping rather than sprints and stand-ups.

Question 14Digital Technologies (content domains not enumerated in source)

A binary search is performed on a sorted array of 1024 elements. Approximately how many comparisons are needed in the worst case?

  1. 10 Correct answer.
  2. 1024
  3. 512
  4. 32

Explanation

Binary search halves the search space each step, so the worst case is about log base 2 of 1024, which equals 10 comparisons. Linear scanning would need up to 1024 comparisons, and 512 or 32 do not match the halving behaviour.

Question 15Digital Technologies (content domains not enumerated in source)

Which statement correctly distinguishes lossless from lossy compression?

  1. Lossless compression restores the original data exactly; lossy does not Correct answer.
  2. Lossy compression is reversible if the original is retained
  3. Lossless compression only works on text files
  4. Lossy compression always produces smaller files than lossless compression

Explanation

Lossless compression allows the original data to be reconstructed exactly, while lossy compression discards some information permanently to achieve smaller sizes. File size comparisons depend on the data, lossless methods apply to many media types, and lossy compression is not reversible.

Question 16Digital Technologies (content domains not enumerated in source)

A company stores backups on a remote server and also on a local drive, and tests restoration monthly. Which aspect of information security does the monthly test primarily address?

  1. Authentication through passwords
  2. Confidentiality through encryption
  3. Availability through verified recovery Correct answer.
  4. Non-repudiation through logging

Explanation

Testing restores confirms that data can actually be recovered after loss, which supports availability. Encryption supports confidentiality, logging supports non-repudiation, and passwords support authentication, none of which the restore test directly verifies.

Question 17Digital Technologies (content domains not enumerated in source)

In an object-oriented program, a class 'Shape' has a method 'area()', and subclasses 'Circle' and 'Square' each provide their own version. What is this called?

  1. Abstraction
  2. Encapsulation
  3. Inheritance
  4. Polymorphism Correct answer.

Explanation

Polymorphism lets objects of different subclasses respond to the same method call with their own implementation, so area() behaves appropriately for each shape. Inheritance is the mechanism that creates the subclasses, encapsulation hides internal state, and abstraction exposes simplified interfaces.

Question 18Digital Technologies (content domains not enumerated in source)

A user's password is stored as a salted hash. Why is the salt added before hashing?

  1. It ensures identical passwords produce different stored hashes Correct answer.
  2. It replaces the need for a secure hashing algorithm
  3. It encrypts the password so it can be decrypted later
  4. It reduces the length of the stored value

Explanation

A unique salt per user means the same password hashes to different values, defeating precomputed rainbow tables and hiding duplicate passwords. Hashing is one-way so nothing is decrypted, salts add rather than reduce length, and a strong hashing algorithm is still required.

Question 19Digital Technologies (content domains not enumerated in source)

A network uses a star topology with a central switch. What happens to the network if one workstation's cable fails?

  1. All workstations lose connectivity but the switch keeps running
  2. The entire network fails
  3. The switch automatically reroutes traffic through other workstations
  4. Only that workstation loses connectivity Correct answer.

Explanation

In a star topology each device has its own link to the central switch, so a single cable failure isolates only the affected workstation. The switch continues serving other devices, and traffic is not routed through workstations.

Question 20Digital Technologies (content domains not enumerated in source)

A program uses a recursive function to compute Fibonacci numbers without memoisation. Why does it perform poorly for larger inputs?

  1. It recomputes the same subproblems many times Correct answer.
  2. It uses too little stack memory
  3. It cannot handle integer values
  4. It requires the input to be sorted

Explanation

Naive recursion recomputes overlapping subproblems repeatedly, causing execution time to grow exponentially. Memoisation or iteration removes the duplication. The issue is excess stack use rather than too little, and sorting is irrelevant to Fibonacci.

Question 21Digital Technologies (content domains not enumerated in source)

A system must process 10 million records within a fixed time budget, and two algorithms are candidates: one with O(n log n) and one with O(n squared) complexity. Which reasoning supports choosing the O(n log n) algorithm?

  1. It guarantees a sorted output
  2. It always uses less memory than the other algorithm
  3. It avoids the need for testing
  4. Its growth rate is lower, so it scales better as n increases Correct answer.

Explanation

Big-O describes how running time grows with input size, so an O(n log n) algorithm scales far better than an O(n squared) one for large n. Complexity notation says nothing about memory use, output ordering, or testing needs.

Question 22Digital Technologies (content domains not enumerated in source)

A distributed database must remain available during a network partition. According to the CAP theorem, which property must be relaxed?

  1. Availability
  2. Durability
  3. Partition tolerance
  4. Consistency Correct answer.

Explanation

CAP states that a distributed system facing a partition can guarantee only two of consistency, availability, and partition tolerance. Since partitions must be tolerated in a distributed system, choosing availability means relaxing strong consistency. Durability is not part of CAP.

Question 23Digital Technologies (content domains not enumerated in source)

A team collects analytics on how users navigate an interface, then iteratively refines the design based on observed behaviour. Which design approach does this best reflect?

  1. Waterfall requirements specification
  2. Feature-driven development without user input
  3. User-centred design informed by usability testing Correct answer.
  4. Security threat modelling

Explanation

Gathering evidence about real user behaviour and iterating on the design is central to user-centred design supported by usability testing. Waterfall fixes requirements up front, feature-driven development focuses on feature delivery, and threat modelling addresses security risks rather than usability.

Question 24Digital Technologies (content domains not enumerated in source)

An algorithm processes a list of n items and, for each item, performs a binary search over the same list. What is the overall time complexity?

  1. O(n)
  2. O(n log n) Correct answer.
  3. O(n squared)
  4. O(log n)

Explanation

A binary search costs O(log n) per lookup, and it is performed once for each of the n items, giving O(n log n) overall. O(n) would apply if each lookup were constant time, O(log n) if only one search occurred, and O(n squared) if each item required a full linear scan.

Question 25Digital Technologies (content domains not enumerated in source)

A developer must choose between storing session state on the server and storing a signed token on the client. Which trade-off most accurately describes the client-token approach?

  1. It guarantees the token cannot be stolen
  2. It scales across servers more easily but revocation is harder Correct answer.
  3. It eliminates the need for HTTPS
  4. It removes the need for any signature verification

Explanation

A stateless signed token lets any server verify the client without shared session storage, which scales well, but invalidating an issued token before expiry is difficult without extra infrastructure. The token still requires signature verification, can be stolen if exposed, and must be protected in transit by HTTPS.

Question 26Digital Technologies (content domains not enumerated in source)

A digital media project must deliver a 4K video to users on slow rural connections. Which design decision best reflects the principle of designing for the intended end user context?

  1. Require users to download the entire file before playback begins
  2. Deliver only the highest-quality 4K file to preserve visual fidelity
  3. Provide adaptive bitrate streaming with multiple resolution renditions Correct answer.
  4. Assume all users have fibre and optimise solely for 4K quality

Explanation

Designing for end-user context means matching the delivery method to real constraints such as bandwidth and device capability. Adaptive bitrate streaming selects a rendition the connection can sustain, so playback remains usable across varied conditions.

Question 27Digital Technologies (content domains not enumerated in source)

In a relational database, a foreign key in an orders table references the primary key of a customers table. What integrity guarantee does this constraint provide?

  1. Every order row must reference an existing customer row Correct answer.
  2. Customer rows are deleted whenever their orders are removed
  3. Order rows are automatically sorted by customer identifier
  4. Each customer may appear in at most one order row

Explanation

A foreign key enforces referential integrity: a value in the referencing column must match an existing key value in the referenced table, or be null if permitted. This prevents orphaned order records pointing at nonexistent customers.

Question 28Digital Technologies (content domains not enumerated in source)

A student writes a Python loop that appends items to a list while also iterating over that same list. Why can this produce unexpected results?

  1. Mutating a collection during iteration can skip or repeat elements Correct answer.
  2. Appending to a list always raises an exception in Python
  3. Python lists cannot store more than one data type at a time
  4. The loop variable is read-only and cannot be reassigned

Explanation

Iteration relies on an internal position that advances through the collection; changing its length mid-loop shifts the remaining elements relative to that position. Elements can therefore be skipped or visited twice, producing logic errors that are hard to trace.

Question 29Digital Technologies (content domains not enumerated in source)

Which statement best describes the role of a content management system (CMS) in producing a digital outcome?

  1. It compiles source code into machine instructions for the server
  2. It automatically designs the visual layout without human input
  3. It encrypts all traffic between the browser and the server
  4. It separates stored content from presentation so non-developers can update pages Correct answer.

Explanation

A CMS stores content in a structured repository and renders it through templates, decoupling authoring from code. This lets content editors publish and revise material without editing source files.

Question 30Digital Technologies (content domains not enumerated in source)

A digital outcome must meet the needs of users with colour vision deficiency. Which design choice most directly supports this?

  1. Use red and green exclusively to signal success and failure
  2. Reduce the contrast between foreground and background
  3. Pair colour cues with text labels or distinct shapes Correct answer.
  4. Increase the saturation of all status colours

Explanation

Colour should never be the sole carrier of meaning, because some users cannot distinguish certain hues. Adding text or shape redundancy ensures the information survives for users with colour vision deficiency.

Question 31Digital Technologies (content domains not enumerated in source)

In a software project, what is the purpose of writing unit tests alongside the code?

  1. To replace the need for any user acceptance testing
  2. To measure how many lines of code each developer has written
  3. To guarantee the program contains no security vulnerabilities
  4. To verify individual components behave as specified and catch regressions Correct answer.

Explanation

Unit tests exercise small units such as functions in isolation, checking that outputs match expectations. Running them repeatedly after changes detects regressions early, before defects reach later stages.

Question 32Digital Technologies (content domains not enumerated in source)

A program stores a user's age in a variable. Which data type is most appropriate for an age measured in whole years?

  1. Boolean
  2. String
  3. Integer Correct answer.
  4. Floating-point number

Explanation

Whole-year ages are discrete counts, so an integer type stores them exactly and supports arithmetic and comparison directly. Choosing the natural type avoids unnecessary conversions later.

Question 33Digital Technologies (content domains not enumerated in source)

A team is choosing a file format for a photographic image that will be edited repeatedly across sessions. Which format characteristic matters most?

  1. Lossless storage that preserves all pixel data across edits Correct answer.
  2. Maximum compression regardless of quality loss
  3. Smallest possible file size for web delivery
  4. Embedding executable scripts inside the image

Explanation

Repeated editing compounds compression artefacts, so a lossless format preserves quality through multiple save cycles. Lossy formats degrade further each time they are re-encoded.

Question 34Digital Technologies (content domains not enumerated in source)

A recursive function lacks a correct base case. What is the most likely consequence when it is called?

  1. It automatically converts itself into an iterative loop
  2. It returns the correct result but more slowly than an iterative version
  3. It recurses until the call stack overflows and the program crashes Correct answer.
  4. It returns a null value to the caller without error

Explanation

A base case terminates recursion; without one, each call adds a new stack frame indefinitely. The runtime eventually exhausts the stack and raises an overflow or recursion error.

Question 35Digital Technologies (content domains not enumerated in source)

Two functions solve the same problem: one runs in O(n^2) time and the other in O(n log n). For very large n, which statement is accurate?

  1. Complexity classes describe memory use only, not execution time
  2. The O(n log n) function grows more slowly and will be faster for large inputs Correct answer.
  3. Both functions take identical time because they solve the same problem
  4. The O(n^2) function is always faster because it has fewer operations per step

Explanation

Big-O describes how running time grows with input size, and n log n grows more slowly than n squared. For sufficiently large n the lower-growth function performs fewer operations overall.

Question 36Digital Technologies (content domains not enumerated in source)

A web form accepts a filename from the user and uses it directly to build a server file path. Which risk is most directly created?

  1. Man-in-the-middle interception of the connection
  2. Path traversal allowing access to files outside the intended directory Correct answer.
  3. Cross-site scripting executing in the user's browser
  4. Denial of service through oversized request headers

Explanation

If user input is concatenated into a file path without validation, sequences that climb directories can escape the intended folder. This is path traversal, and it can expose or overwrite sensitive files.

Question 37Digital Technologies (content domains not enumerated in source)

A system uses a checksum alongside each transmitted data packet. What does the checksum allow the receiver to detect?

  1. Whether the sender's clock is synchronised
  2. Accidental corruption of the packet contents during transmission Correct answer.
  3. Deliberate tampering by an attacker with the secret key
  4. The physical distance the packet travelled

Explanation

A checksum is a computed value derived from the data and sent with it; the receiver recomputes and compares. A mismatch signals that bits changed in transit, typically through noise or faults.

Question 38Digital Technologies (content domains not enumerated in source)

A development team adopts continuous integration. Which practice is central to this approach?

  1. Writing all tests only after the product has shipped
  2. Requiring manual deployment of every change by one designated person
  3. Freezing the main branch until the final release date
  4. Merging code changes frequently and running automated builds and tests on each merge Correct answer.

Explanation

Continuous integration means developers integrate work often, with automated build and test pipelines validating each change. This surfaces integration defects early when they are cheap to fix.

Question 39Digital Technologies (content domains not enumerated in source)

A relational table has a column that stores a comma-separated list of phone numbers for each customer. Why does this design create problems?

  1. It uses too many columns for the database engine to handle
  2. It stores repeating groups in one field, making queries and updates difficult Correct answer.
  3. It prevents the table from having a primary key at all
  4. It forces every value in the table to be stored as text

Explanation

Storing multiple values in a single field violates first normal form and makes searching, updating, or deleting an individual number awkward. A separate table linked by a foreign key models the one-to-many relationship properly.

Question 40Digital Technologies (content domains not enumerated in source)

A company wants to ensure that a software update genuinely came from its vendor and was not altered in transit. Which mechanism addresses this?

  1. A checksum published on the same download page
  2. Renaming the file with a version number
  3. Compressing the update into an archive
  4. A digital signature verified with the vendor's public key Correct answer.

Explanation

A digital signature binds the update to the vendor's private key, and verification with the public key confirms both origin and integrity. Any alteration invalidates the signature.

Question 41Digital Technologies (content domains not enumerated in source)

In an agile project, what is the main purpose of a retrospective at the end of a sprint?

  1. To reflect on team process and agree on improvements for the next sprint Correct answer.
  2. To demonstrate completed features to stakeholders for feedback
  3. To assign individual blame for defects found during the sprint
  4. To estimate the effort required for upcoming backlog items

Explanation

A retrospective focuses on how the team works, identifying process issues and actions to improve. Demonstrating features and estimating work are handled by other ceremonies such as reviews and planning.

Question 42Digital Technologies (content domains not enumerated in source)

A web page loads a large JavaScript file that blocks rendering in the page head. Which change most directly improves perceived load performance?

  1. Move the script to the very top of the head section
  2. Load the script with the defer attribute so parsing continues first Correct answer.
  3. Remove all CSS from the page to reduce total bytes
  4. Increase the size of the script by adding comments

Explanation

A classic script in the head pauses HTML parsing while it downloads and executes. Using defer lets the parser continue and runs the script after the document is parsed, improving perceived responsiveness.

Question 43Digital Technologies (content domains not enumerated in source)

A program must store a set of unique tags and quickly test whether a tag is already present. Which data structure is most suitable?

  1. A queue that processes tags first in, first out
  2. An unsorted list searched linearly each time
  3. A hash set with average constant-time membership testing Correct answer.
  4. A stack that pushes and pops tags in order

Explanation

A hash set stores unique keys and supports average constant-time membership checks, which matches the requirement. Linear search over a list costs time proportional to its size on each lookup.

Question 44Digital Technologies (content domains not enumerated in source)

A mobile app must work offline and later synchronise changes with a server. Which design consideration is most important?

  1. Disabling all local caching to reduce storage use
  2. Requiring a constant network connection to function
  3. Handling conflicts when the same record is changed locally and remotely Correct answer.
  4. Ensuring the app never stores any data on the device

Explanation

Offline-first designs let users modify data without connectivity, so the same record may change in two places before syncing. A defined conflict resolution strategy prevents data loss or inconsistency when changes merge.

Question 45Digital Technologies (content domains not enumerated in source)

A team uses a distributed version control system with feature branches. What is the main benefit of merging through a reviewed pull request?

  1. Changes are inspected by others before entering the shared main branch Correct answer.
  2. Each developer's commits are automatically reverted after merging
  3. The repository no longer needs any commit history
  4. Branching is disabled once the first pull request is opened

Explanation

A pull request creates a point where peers can review, discuss, and test proposed changes before they join the mainline. This catches defects and shares knowledge before integration.

Question 46Digital Technologies (content domains not enumerated in source)

An algorithm must find the shortest path from one node to all others in a graph with non-negative edge weights. Which approach is appropriate?

  1. A linear scan of the adjacency matrix only
  2. Depth-first search recording visit order
  3. Breadth-first search ignoring edge weights
  4. Dijkstra's algorithm using a priority queue Correct answer.

Explanation

Dijkstra's algorithm greedily expands the nearest unvisited node, which is correct when weights are non-negative. A priority queue keeps the next-closest node efficient to select.

Question 47Digital Technologies (content domains not enumerated in source)

A system design must tolerate the failure of any single server while continuing to serve reads. Which approach best supports this?

  1. Caching responses only in the client browser
  2. Storing all data on one high-specification server
  3. Replicating data across multiple servers with automatic failover Correct answer.
  4. Running a single server with a longer backup interval

Explanation

Replication places copies of data on several servers so that losing one still leaves others able to answer reads. Automatic failover redirects traffic to a healthy replica, maintaining availability.

Question 48Digital Technologies (content domains not enumerated in source)

A function processes a list of n records and, for each record, performs a constant-time hash lookup. What is the overall time complexity?

  1. O(n^2)
  2. O(log n)
  3. O(1)
  4. O(n) Correct answer.

Explanation

The loop runs once per record, giving n iterations, and each iteration does a constant-time hash lookup. Multiplying a linear count by constant work yields O(n).

Question 49Digital Technologies (content domains not enumerated in source)

A database experiences slow queries on a large table filtered by a column that is rarely selective. Which action is most likely to improve performance?

  1. Analyse the query plan and add a suitable index or rewrite the filter Correct answer.
  2. Remove all indexes so writes become faster
  3. Add more columns to the table to spread the data
  4. Increase the length of the column names

Explanation

Examining the execution plan shows whether a full scan is occurring and why. Adding an appropriate index or restructuring the query can then reduce the rows examined.

Question 50Digital Technologies (content domains not enumerated in source)

A team must choose between a relational database and a document store for data whose schema changes frequently per record. Which reasoning is strongest?

  1. A relational database removes the need for any schema design
  2. A document store guarantees stronger referential integrity
  3. A document store accommodates varying record shapes without migrations Correct answer.
  4. A relational database cannot store any variable data

Explanation

Document stores hold self-describing records, so records with differing fields can coexist without a schema migration. Relational databases favour a stable, enforced schema and strong integrity constraints.