Databricks interview questions for engineers

Topic tags
Python
Storage & state

Reported interview periodNov 2025–Aug 2026

Rolling Request Load and QPS

Build a counter that records requests by timestamp and reports request load or queries per second over a trailing window.

Practice focusRequirements - Timestamps are non-negative non-boolean integer seconds and arrive in non-decreasing order. Reject invalid or decreasing timestamps with ValueError before changing state. - Multiple requests may have the same timestamp. - Current time is the latest timestamp observed. - A window of seconds includes events satisfying now - seconds < t <= now . - Both queries require a positive non-boolean integer seconds , otherwise raise ValueError . get qps is load divided by seconds . Before any hits, both return zero.…

Free practice

Topic tags
Python
Data structures
Storage & state
Data / SQL

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Jul 2026

Snapshot Iterator over a Mutable Set

Implement an insertion-ordered mutable set whose iterators observe a stable snapshot even as the live set changes.

Practice focusRequirements - Iteration follows current insertion order at iterator creation time. - Adding an already-present value changes nothing. - Removing and later re-adding a value places it at the end of the live order. - contains reflects current state, while an existing iterator continues to return exactly its snapshot. - next raises StopIteration after exhaustion. - Removing an absent value is a no-op. has next never advances an iterator, including repeated checks after exhaustion. Independent iterators have independent cursors.…

Free practice

Topic tags
Python
Data structures

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Jul 2026

Paths in an Implicit Fibonacci Tree

Define a Fibonacci tree of order k as a root whose left subtree has order k-1 and whose right subtree has order k-2. Nodes are labeled by their one-based preorder position. Compute paths without materializing t…

Practice focusRequirements - Use tree size(k) = F(k+2) - 1 , with F(0)=0 and F(1)=1 . - fib path returns node labels from start to end , inclusive. - fib directions returns "Up" steps to the lowest common ancestor, then "Left" or "Right" steps downward. - Validate that labels lie within the requested tree. - Order zero is an empty tree, order one is a single root, and subtrees of order zero or below are empty. Public orders must be non-negative non-boolean integers; labels must be non-boolean integers in 1..tree size(order) .…

Free practice

Topic tags
Python
Algorithms

DatabricksCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodMay 2026

Partition a Target into Source Substrings

Given a source string and a target string, represent the target as the fewest contiguous substrings copied from the source. Return the inclusive source range used for each target piece, in target order.

Practice focusAssumptions Ranges are zero-based and inclusive. If the target cannot be covered, return [] ; an empty target also returns [] . Among solutions with the fewest pieces, prefer the longest possible next piece, then the leftmost matching source range. For example, min partitions("abcdbcd", "dabcd") returns [[3,3], [0,3]] . min partitions after delete removes target[index] and solves the same problem; the index must be an integer (not a boolean) from zero through len(target)-1 . Invalid indices raise IndexError .…

Free practice

Topic tags
Python
Distributed systems

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–May 2026

Uniform Random Connection Across Node Groups

Given disjoint non-empty groups of node IDs, treat each group as an internally connected component. Generate a random set of additional edges connecting all groups, never joining two nodes from the same group. …

Practice focusRequirements - Return exactly len(groups) - 1 edges when there is more than one group. - Each edge joins nodes from different groups, and all groups become connected. - Use the supplied seed for reproducibility. - Store each edge with the smaller node ID first and return edges in sorted order. - Duplicate node IDs across groups are invalid. - Node IDs are non-boolean integers and seed is a non-boolean integer. Empty input returns [] ; empty groups, duplicate IDs within or across groups and invalid IDs/seeds raise ValueError before sampling.…

Free practice

Topic tags
Python
Data / SQL

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026–Apr 2026

Lazy Array Transformations

Implement an immutable-style array wrapper whose transformations are deferred until a terminal operation needs values.

Practice focusRequirements - map returns a new LazyArray and must not invoke the function immediately. - Chained maps apply in declaration order. - index of evaluates original elements from left to right, stopping at the first transformed value equal to target ; return that original index or -1 . - Branches sharing a prefix must not mutate or otherwise affect each other. - Avoid evaluating elements after a match is found. - Construction snapshots the finite input sequence. Later mutations of the caller's list do not change this wrapper or its branches.…

Free practice

Topic tags
Python
Data / SQL

DatabricksCodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodJan 2026

Safe Filter Pushdown in a Query Plan

Implement a small optimizer pass that pushes filters closer to scans when doing so preserves query semantics.

Practice focusAssumptions Use these immutable-style dictionary nodes: - {"op":"scan", "table":..., "columns":[...]} - {"op":"filter", "column":..., "child":...} - {"op":"project", "columns":[...], "child":...} - {"op":"join", "how":"inner"|"left", "left":..., "right":...} Requirements - Push a filter through a projection only if the filtered column remains available. - Push into the unique side exposing that column for an inner join. - For a left join, a filter may push into the preserved left side.…

Free practice

Topic tags
Python
Algorithms

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025

Largest All-Ones Square and Rectangle

Given a binary matrix containing characters '0' and '1', return the area of the largest axis-aligned region containing only ones.

Practice focusImplementation requirements 1. Implement maximal square . An empty matrix or a matrix containing no ones returns 0 . 2. Extend the solution to maximal rectangle , where height and width may differ. Inputs are rectangular lists of rows containing only the strings '0' and '1' ; empty matrices and zero-column matrices return 0 . Return an integer area without modifying the input. Malformed rows are outside the assessed input contract. Target O(rows cols) time.…

Free practice

Topic tags
Python
Communication

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025

Maximum Non-Conflicting Robbery Value

Given non-negative values associated with houses, select a subset with maximum total value subject to adjacency constraints.

Practice focusImplementation requirements 1. Linear street: adjacent houses cannot both be selected. For example, rob([1,2,3,1]) == 4 . 2. Circular street: the first and last houses are adjacent. A single house may be selected. 3. Tree neighborhood: each node is a dictionary with a non-negative integer val and optional left and right child dictionaries (absent or None means no child). Selecting a node forbids its children. The input is a finite acyclic binary tree, not a shared-node graph. 4.…

Free practice

Topic tags
Python
Concurrency
Product design

DatabricksCoding

Talk-through codingNo local grader

Reported interview periodOct 2025

Thread-Safe Channel Chat

Implement an in-memory chat service in which users subscribe to channels, messages are appended to channel histories, and users read messages from their current subscriptions.

Practice focusRequirements - Methods may run concurrently and shared state must be protected explicitly. - Sending appends [channel id, user id, message] even if the sender is not subscribed. - Reading concatenates histories for the user's current subscriptions in sorted channel-id order; each channel remains in send order. - Unsubscribing hides that channel's history from subsequent reads. - Repeated subscribe or unsubscribe operations should be idempotent. - Define the consistency point of each operation and avoid exposing partially written messages.…

New public brief

Topic tags
Python

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Sep 2026

Generalized Tic-Tac-Toe

Implement a two-player game on a rows x cols board. A player wins by placing k consecutive marks horizontally, vertically, or along either diagonal.

Practice focusRequirements - Player 1 moves first and players alternate. - move places the current player's mark and returns that player number if the move completes a run of length k ; otherwise return 0 . - After a win, later calls return the existing winner without changing it. - Initially assume coordinates are valid and empty; explain how production code would reject invalid moves. - Support rectangular boards and k smaller than either dimension. - Avoid scanning the entire board after every move.…

New public brief

Topic tags
Python

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Sep 2026

Revenue Tracking with Direct Referrals

Build a customer revenue index. Each inserted customer has personal revenue and may name an existing customer as a referrer. A customer's total revenue is personal revenue plus the personal revenue of direct re…

Practice focusRequirements - Assign IDs starting at 0 in insertion order. - If a referrer is provided, update that customer's total by the new customer's personal revenue. - A customer's referrals do not contribute to its referrer's total; attribution is one level only. - The query considers totals at least min total revenue , orders by (total revenue, id) , and returns at most k IDs. - Validate non-negative revenue, valid referrers, and non-negative k .…

New public brief

Topic tags
Python
Data structures
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Minimize Encryption Work in a File Tree

A file hierarchy contains directories and files. Some files are already encrypted. You may encrypt an individual file or issue one recursive encryption request for an entire directory. Choose operations with mi…

Practice focusRequirements and cost model - Encrypting one file costs t req + t file . - Encrypting a directory costs t req + N t file , where N is every file in its subtree, including already-encrypted files. - A subtree with no unencrypted files costs 0 . - At a directory, you may batch the whole subtree or solve its children independently. count files returns (encrypted count, unencrypted count) . The input is a finite tree of FileNode and DirectoryNode objects, with boolean encryption flags, no cycles or shared nodes, and non-negative integer costs.…

New public brief

Topic tags
Python
Algorithms
Concurrency

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Choose the Best Transit Mode Through a Grid

A grid contains a start S, a destination D, blocked cells, and cells labeled by transit mode. A trip must use one mode for its entire route. Choose the reachable mode with the best travel time and cost.

Practice focusRequirements - Digit '1' identifies modes[0] , digit '2' identifies modes[1] , and so on. - Movement is allowed in four cardinal directions through cells of the chosen digit. - S and D may be entered for free and add neither time nor cost. - X , unrelated mode digits, and any other symbols are blocked. - For a route using mode i , each mode cell contributes times[i] and costs[i] . - Choose minimum total time, then minimum total cost, then earlier position in modes . Return "" if no mode reaches D .…

New public brief

Topic tags
Python
Distributed systems
Storage & state
Reliability

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Circuit Breaker and Replica Failover

Implement a circuit breaker that protects a dependency after repeated failures, then use it to route work across database replicas.

Practice focusRequirements - CLOSED permits calls. A success resets the consecutive-failure count. - After failure threshold consecutive supplier failures, transition to OPEN and propagate the failure. - While OPEN , reject calls without invoking the supplier. - Raise the provided CircuitOpenError for breaker-generated denial; propagate supplier errors unchanged. An error message containing the word OPEN is not a denial signal. - After recovery timeout , permit one HALF OPEN probe. Success closes the breaker; failure reopens it and restarts the timeout.…

Public brief

Topic tags
Python
Algorithms
Data / SQL

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Anagrammed Substring Search

Given a text and a query, find the first position at which a substring of the text is an anagram of the query. Two strings are anagrams when they contain the same characters with the same multiplicities, regard…

Practice focusRequirements Implement: Return the zero-based start index of the first matching window, or -1 when no match exists. An empty query matches at index 0 ; a query longer than the text has no match. Characters are initially compared exactly, including case. Aim for O(n + m) time for a text of length n and query of length m , rather than sorting every window. Additional assessed interfaces 1. Return every matching start index. For an empty query, return every boundary from 0 through len(lookup string) . 2.…

Public brief

Topic tags
Python
Algorithms
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Aug 2026

Delete a Position from Interval Coverage

A compact coverage set is represented by sorted, non-overlapping, non-touching inclusive intervals. If the covered values were expanded into one ordered sequence, delete the value at a given zero-based position…

Practice focusFor example, [(4, 7), (10, 11), (13, 15)] represents 4,5,6,7,10,11,13,14,15 . Deleting position 2 removes value 6 , producing [[4, 5], [7, 7], [10, 11], [13, 15]] . Requirements - Return intervals as [start, end] pairs. - Preserve sorted, non-overlapping, non-touching output. - A deletion may shrink an endpoint, remove a singleton interval, or split an interval in two. - Assume index refers to an existing covered value; state how you would report an invalid index. - Do not expand every covered integer when ranges may be large.…

Public brief

Topic tags
Python
Concurrency
Reliability

DatabricksCoding

Talk-through codingNo local grader

Reported interview periodNov 2025–Aug 2026

Durable Multi-Threaded Log Writer

Implement a log writer that accepts binary records from multiple threads and durably appends each complete record to a file.

Practice focusRequirements - Encode each record as a four-byte big-endian length followed by its payload. - push returns only after all bytes for that record are written and the file is synchronized to durable storage. - A record's bytes must never interleave with another record. - Calls from one thread retain program order; calls from different threads may appear in either order. - close must coordinate with active or future pushes and be idempotent. - Handle partial writes, I/O errors, and payload lengths that cannot be represented.…

Public brief

Topic tags
Python
Concurrency

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Hybrid Run-Length and Bit-Packing Codec

Implement a reversible encoder for an integer sequence using run-length blocks for long runs and fixed-size literal blocks otherwise.

Practice focusRequirements and format - A run of at least eight equal values becomes ["RLE", value, count] and consumes the full run. - Otherwise consume the next eight values as ["BP", values] . - A final block may contain fewer than eight values. If every remaining value is equal, encode it as RLE; otherwise use a short BP block. - Walk strictly left to right, making output deterministic. decode must validate the entire block sequence before reconstructing it.…

Public brief

Topic tags
Python
Networking
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Aug 2026

Ordered IPv4 Firewall Rules

Implement an ordered firewall policy for IPv4 addresses.

Practice focusEach rule is [action, cidr] , where action is "ALLOW" or "DENY" . Evaluate rules from top to bottom; the first network containing the address determines the result. If no rule matches, deny access. A rule without a prefix length represents one address, equivalent to /32 . Requirements - Parse and validate dotted-decimal IPv4 addresses and CIDR prefix lengths. - Correctly handle /0 , /32 , network boundaries, and overlapping rules. - Preserve first-match semantics; a more specific later rule does not override an earlier match.…

Public brief

Topic tags
Python
Data structures

Coding exerciseCoding

Written response35 minutes

Reported interview periodN/A

Grade book

An in-memory grade book with a ranking that does not treat a missing score as zero.

Practice focusState, Ranking, Edge cases through a written response exercise.

Public brief

Topic tags
Python
Algorithms

Coding exerciseCoding

Written response35 minutes

Reported interview periodN/A

Vial log

Return the vials that stayed inside a temperature range for their whole stay.

Practice focusScanning, Missing data through a written response exercise.

Public brief

Topic tags
Python
Algorithms

Coding exerciseCoding

Written response35 minutes

Reported interview periodN/A

Comment batches

Collapse consecutive comments on the same path into one batch.

Practice focusOrder, Grouping through a written response exercise.

Public brief

Topic tags
Python
Algorithms
Data structures

Coding exerciseCoding

Written response40 minutes

Reported interview periodN/A

Launch order

Return one valid order of steps, or report a cycle.

Practice focusOrdering, Cycles through a written response exercise.