Bloomberg Senior Software Engineer Interview: Five Rounds, Offer

How the process went

1. Application

   Applied for a Senior Software Engineer role through Bloomberg's careers site; a recruiter followed up within about a week.

2. Screening

   A screening conversation combining a resume-project discussion, a question about motivation for joining Bloomberg, and one coding problem.

3. On-site coding rounds

   Two separate on-site coding interviews, each opening with a discussion of a resume project before a data-structure design question.

4. System design round

   An on-site conversation with a team lead built around a deeper project discussion and a data-pipeline scaling exercise.

5. Recruiter conversation

   A non-technical on-site conversation with a recruiter about team culture, life in London, and the recruiting process.

6. Hiring manager round

   A conversation with the hiring manager focused on motivation for joining Bloomberg and relocating, an overview of the team, and a high-level systems-design exercise.

7. Outcome

   The candidate received an offer, accepted it, and joined.

Screening

Initial screen combining a resume-project discussion and one coding question

• A discussion of one of the candidate's resume projects, lasting about ten minutes.
• Why do you want to join Bloomberg?
• Given a sequence that decreases toward a point and then increases again (a U-shaped array), search for a target value, comparable to the 'Search in Rotated Sorted Array' problem.

On-site Coding Round 1

Project discussion followed by two data-structure design questions

• A discussion of one of the candidate's resume projects, lasting about ten minutes.
• Design an Underground System that tracks customer check-ins and check-outs and computes average travel time between stations.
• A third question, which the candidate's write-up referenced by linking to a separate public account of a Collatz Conjecture problem rather than restating it directly.

On-site Coding Round 2

Discussion of mentorship experience and a constant-time data-structure design question

• A discussion of the candidate's experience mentoring interns and a project they had driven.
• Design an app-store class that can insert, look up, and delete apps in a registry in constant time, comparable to the 'Insert Delete GetRandom O(1)' problem.

System Design (with Team Lead)

Extended project deep-dive and a data-pipeline scaling exercise

• A deep discussion of one of the candidate's resume projects, lasting about twenty minutes.
• Given a sample data pipeline that ingests parquet files through a Kafka queue and writes to S3 storage, how would you scale it to handle roughly a million small files a day?
• How would the design change if it instead had to handle a few hundred very large files a day?
• How can a single node be kept from running out of memory while processing this pipeline?
• Where are the single points of failure in this system?

Per the candidate's own account, their answers were: add more Kafka consumers to scale horizontally for the many-small-files case; note that extra consumers add little value and risk out-of-memory errors for the few-large-files case; and shard files with something like Spark before handing them to workers to bound per-node memory use.

Recruiter Conversation

Non-technical conversation about culture and relocation logistics

• No technical questions; the conversation covered work culture, life in London, and the recruiting process.

Hiring Manager

Motivation-focused conversation, team overview, and a high-level systems-design exercise

• Why do you want to join Bloomberg?
• If you want to use your finance experience, why not join a different company instead?
• If you're looking for international experience, why not apply to a technology company in the UK instead?
• Why do you want to relocate to London?
• Sketch a high-level architecture for an alerts system for securities.

The hiring manager also described the team's role within the organization and how it functions as a whole before moving to the design exercise.

Source

The questions and process facts come from the candidate's public write-up, linked below. The retelling above is our own summary.