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Bloomberg interview notes, page 7 of 14

Large Enterprises

Most of these Bloomberg write-ups come from Software Engineers (130), then Product Managers (2) and Data Analysts (1). The most reported rounds are the technical phone screen (100), the behavioral / leadership round (8), the onsite coding round (8) and the system design round (8).

133 interview notes · updated Oct 2026

Bloomberg·Software Engineer·Onsite - Behavioral / Leadership

May 2026
Behavioral screen for a Software Engineer role at Bloomberg. Pretty standard format: walk through your background, pick a project to dissect, and explain why Bloomberg specifically. Nothing that should blindside you if you've done a few of these.
  • Give a brief overview of your background and highlight a couple of projects you've worked on.
  • Pick one project and walk through the problem, what you personally owned, the technical decisions you made, the trade-offs involved, and what the outcome was.
  • Why do you want to work at Bloomberg specifically, and what draws you to this role?

“I always fumble the opener.”

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Bloomberg·Software Engineer·Technical Phone Screen

May 2026
Bloomberg SWE interview that leaned heavily on graph traversal. The whole session was basically one problem stretched across five angles, which I didn't expect. Left feeling okay about the core solution but shaky on some of the follow-ups.
  • Given an m x n grid of '1's (land) and '0's (water), count the number of distinct islands where connectivity is 4-directional only. Implement a solution running in O(m*n) time and explain why it's correct.
  • Re-implement the island count using an explicit BFS with an iterative queue instead of recursion. How does the complexity compare to your DFS solution?
  • How does your solution handle edge cases like a null grid, all-water grid, single-cell grid, fully-land grid, very large grids, and diagonal-only touching cells?
  • Describe or write tests that validate your solution on several nontrivial inputs, including the 3-island example from the problem.
  • How would you modify your solution if diagonal adjacency (8-directional) also counted as connected?

“I went with DFS and flood-fill, which felt natural.”

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Bloomberg·Software Engineer·Technical Phone Screen

Jun 2026
Bloomberg SWE interview, got a linked list merging problem. Pretty standard stuff for this type of role but the k-list variant has enough edge cases to trip you up if you're not careful.
  • Given an array of k sorted linked lists, merge them all into a single sorted linked list and return its head.

“The naive approach works but they're probably watching to see if you jump straight to a priority queue or think through it first.”

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Bloomberg·Software Engineer·Technical Phone Screen

Jun 2026
Bloomberg coding round, one design question the whole time. Pretty focused session, they wanted both the concept and a working implementation before the clock ran out.
  • Design and implement a data structure that supports adding a participant, removing a participant, and picking a uniformly random participant, with all three operations running in O(1) average time.

“I knew the hash map piece pretty fast but kept second-guessing the array side.”

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Bloomberg·Software Engineer·Technical Phone Screen

Jun 2026
Bloomberg coding round, one question, stack-based string decoding. Not a brutal interview but the edge cases are where they really watch you.
  • Given an encoded string in the format k[encoded_string], write a function to decode it. For example, '3[a2[c]]' should return 'accaccacc'.

“I got the basic idea pretty fast, stack of (count, string) pairs, push on '[', pop and expand on ']'.”

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Bloomberg·Software Engineer·Technical Phone Screen

Jun 2026
Bloomberg data engineering interview, technical phone screen or take-home style question involving some gnarly PostgreSQL string parsing. One question, no fluff, just raw SQL and a lot of edge cases to think through.
  • Given a PostgreSQL clickstream table with URL and semicolon-delimited query columns, write a single SELECT that extracts the registrable domain and first path segment from the URL, pulls a specific query parameter from the URL, parses two UTM fields from the semicolon-delimited column (case-insensitive, trimmed, NULL if missing), lowercases all string outputs, and filters to a specific date range. Core string/regex functions only, no JSON or external extensions.

“This one is deceptively wide.”

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Bloomberg·Software Engineer·Onsite - System Design / Architecture

Jun 2026
Bloomberg system design round for a software engineer role. Four connected questions all built around the same 'hello username' app, which sounds trivial until you realize they want full API specs, auth architecture, session security, and a scalable activity-tracking service before you're done.
  • Design the client-server APIs for sign-up, sign-in, sign-out, and fetching a personalized greeting. What are the request and response shapes, status codes, and how do you handle errors?
  • How would you handle authentication: stateful sessions vs. stateless tokens like JWT? Walk through password storage, TLS, CSRF protection, and XSS mitigations.
  • After a user signs in, how do you prevent someone else from impersonating them by reusing or guessing their session identifier? Cover entropy, rotation, expiration, token storage, and defenses against fixation and replay attacks.
  • Design a service that returns the top N most active users over a recent time window. Define what 'active' means, what signals you count, how you model the data, and how you compute it efficiently at scale. Include capacity planning.

“Felt pretty comfortable here since REST API design is bread and butter.”

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Bloomberg·Software Engineer·Technical Phone Screen

Jun 2026
Bloomberg follow-up design question on the bigram next-word predictor. The focus shifted from building the thing to interrogating whether the space complexity was actually necessary, which I wasn't fully prepared for.
  • Your bigram next-word predictor stores full count maps for every prefix. Does it have to use O(N) space relative to total training tokens, and what are your options for reducing that?

“I knew the basic answer (store only the argmax per prefix after training, toss the counts) but then they pushed on what you lose by doing that and I kind of fumbled.”

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Bloomberg·Software Engineer·Technical Phone Screen

Jun 2026
Bloomberg SWE interview with a tree traversal problem that looks straightforward until you actually try to implement it cleanly under pressure.
  • Given the root of a binary tree, return the vertical-order traversal of its node values, grouped by column from leftmost to rightmost, ordered top-to-bottom within each column, and sorted by level-order position when nodes share the same row and column.

“The column tracking clicked pretty fast for me, root at zero, left minus one, right plus one.”

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Bloomberg·Software Engineer·Technical Phone Screen

Jun 2026
Bloomberg SWE interview with a linked list problem that sounds manageable until you actually try to implement it cleanly under pressure.
  • You're given a doubly linked list where each node can have a child pointer leading to another doubly linked list, possibly nested multiple levels deep. Flatten the entire structure into a single doubly linked list where each child list is inserted immediately after its parent node and before the parent's original next node. All child pointers should be null in the result.

“I got the high-level idea pretty fast, like yeah just splice the child list in after the current node and keep going.”

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