Databricks Interview Questions — Page 11

Databricks·Software Engineer·Onsite - System Design / Architecture

May 2026

System design round at Databricks for a software engineer role, basically one big question about building a Slack-style messaging platform from scratch. The scope was enormous and I kept second-guessing whether I was going deep enough on any single piece.

Design a team messaging service similar to Slack, covering workspaces, channels, direct messages, real-time delivery, message history, presence, notifications, search, and file attachments at scale.
How would you handle message ordering guarantees across distributed storage, and what tradeoffs does your approach introduce?
Walk through how you'd scale WebSocket-based fan-out for a channel with tens of thousands of active concurrent members.
How would you design the presence service to show online/offline/away status at scale without overloading your backend?
How would you build search across message history for millions of users and messages?

“This is the kind of question where you can talk for an hour and still feel like you only scratched the surface.”

View Post

Databricks·Software Engineer·Technical Phone Screen

May 2026

Databricks SWE interview with a graph traversal problem that looked like a shortest path question but had a lexicographic twist that tripped me up for a bit. Solid problem, not your average Dijkstra warmup.

Given an m x n grid with a start and destination cell, where each cell holds a value indicating a transport mode (or is blocked), and separate matrices for time and cost to enter each cell, find a path from start to destination using exactly one transport mode that minimizes (total_time, total_cost) lexicographically. Return -1 if unreachable.

“My first instinct was just Dijkstra with (time, cost) as a tuple key and I went with that.”

View Post

Databricks·Software Engineer·Technical Phone Screen

May 2026

Databricks software engineering interview with a meaty systems question about firewall rule matching. The problem started straightforward then got more interesting with the follow-up about range intersection, which is where things got tricky for me.

Design and implement a firewall rule matcher that checks a single IPv4 address against a list of CIDR rules, each tagged as accept or deny. Walk through your choice of data structures and algorithms, then extend the solution to handle an incoming CIDR range instead of a single IP, and discuss efficient approaches for range intersection.

“Started with a trie on the bit representation of the IP, which felt right since CIDR rules are basically prefix matches.”

View Post

Databricks·Software Engineer·Onsite - System Design / Architecture

May 2026

System design round at Databricks for a software engineer role. The whole thing was one big design question about an online bookstore, and they wanted you to go deep on basically everything: requirements, data modeling, scale, payments, the works.

Design an online book-selling platform similar to Amazon Books. Walk through functional requirements, data model, and how you'd handle scale.
How would you handle inventory reservation in this system, and what are the tradeoffs between reserving on add-to-cart versus at checkout?
How would you approach caching and CDN usage for a high-traffic book catalog with heavy read traffic?
How would you design the reviews and ratings feature, and how do you handle eventual consistency there?

“This is a massive question and I underestimated how much they'd push on each layer.”

View Post

Databricks·Software Engineer·Technical Phone Screen

May 2026

Databricks technical screen that went deep into graph theory territory pretty fast. The core problem sounds approachable until you realize the uniformity constraint is basically the whole interview.

You have n disconnected graph components. Write a function that returns a random set of edges that, when added, merges all components into one connected graph. The catch: the edge set must be sampled uniformly at random from all valid solutions. How do you ensure uniform sampling, and why does a naive approach fail?

“I got the basic structure pretty quickly: you need a spanning tree over the components, then pick one endpoint per component per edge.”

View Post

Databricks·Software Engineer·Technical Phone Screen

May 2026

Databricks coding interview for a software engineering role. The problem was a deep dive into compression encoding, specifically building both sides of an RLE/bit-packing hybrid from scratch, plus tests. Pretty involved for a single session.

Implement an encoder and decoder for a hybrid RLE/bit-packing compression format. The encoder receives integers one at a time and must decide which encoding scheme to use based on the input pattern and a minimum-length threshold. The decoder is initialized with the encoder's output and exposes an iterator interface that yields the original integers in order.

“This one took me a while to even fully parse.”

View Post

Databricks·Software Engineer·Onsite - System Design / Architecture

May 2026

Databricks system design round, single question but it ran the full hour. They wanted a deep dive on an in-process cache with LRU eviction, concurrency, and optional durability. More involved than I expected for what sounded like a straightforward caching problem.

Design a single-machine in-memory cache for a web service that supports Get, Put, and Delete operations with LRU eviction and optional durability across restarts.

“Started fine with the hashmap plus doubly-linked list combo for LRU, but the concurrency part is where I started fumbling.”

View Post

Databricks·Software Engineer·Onsite - System Design / Architecture

May 2026

Databricks system design round, one big question about building a distributed key-value store from scratch. Went deep on a lot of moving parts and felt like I was holding on for dear life by the end.

Design a distributed key-value store supporting get, put, and delete on string keys with byte-string values, with optional TTL and compare-and-swap semantics.
How would you handle partitioning and rebalancing as nodes are added or removed from the cluster?
What conflict resolution strategy would you use for concurrent writes, and what are the tradeoffs between vector clocks, last-write-wins, and CRDTs?
How would you implement failure detection across nodes in the cluster?
What storage engine would you use under the hood, and why?

“I started with the API surface which felt safe, but then they immediately pushed on consistency guarantees and I kind of froze for a second.”

View Post

Databricks·Software Engineer·Technical Phone Screen

May 2026

Databricks software engineering interview that went deep into graph algorithms pretty fast. The core problem was shortest path in a transit network, but the real test was how far you could push the extensions.

Given a city modeled as a graph where nodes are locations and edges are transit segments with travel times, find the minimum-time route between two points. How would you approach this, and what algorithm would you use?
How would you extend the shortest-path solution to handle multiple competing criteria, like minimizing travel time versus minimizing the number of transfers?
How would you handle edges whose weights change based on the time of day, like a bus that only runs on a schedule?
How would you update the routing solution in real time as conditions change, for example if a route gets delayed or closed mid-trip?

“Dijkstra, fine, got there.”

View Post

Databricks·Software Engineer·Technical Phone Screen

May 2026

Databricks software engineer interview that threw a recursive tree construction problem at me. The question was more conceptual than I expected and the complexity analysis part is where things got interesting.

Implement a function to construct a Fibonacci tree of order n, where F(0) is empty, F(1) is a single node, and F(n) for n >= 2 has F(n-1) as the left subtree and F(n-2) as the right subtree. Then analyze the time and space complexity of your solution.

“The construction itself wasn't too bad once I mapped out the recursion on paper.”

View Post