The Top 15 Cockroach Labs Interview Questions and How to Answer Them

Interviewing at Cockroach Labs comes with a twist. The interviewing process is unconventional by design—especially for non-engineering positions. The interviews are exercise-based, focused on practical, day-in-the-life style work tasks. Additionally, resumes are removed from the process to fight unconscious bias. People who are used to traditional interviews may find the process a little scary, but it was carefully thought out and is tailored to each job opening. As someone who has recently been through the process, I thought it would be helpful for people who are looking for jobs to hear about my interview and get some insight into it.

For a little context, I joined Cockroach Labs in July as the new Technical Writer. I’ll talk about the interviews from the point of view of a tech writer in this post, but the process is the same for all open jobs at the company.

Most of the time, to get hired as a technical writer, you apply for a job online with your resume and samples of your work. The HR representative conducts a phone interview. If selected, you are called for an in-person interview. The in-person interview generally entails a writing (read: grammar) exercise, followed by routine questions. The interview is usually conducted by two or three tech writers and the hiring manager. From what I’ve seen, most interviews have the candidate tell the hiring team what they can do instead of demonstrating it. This does not necessarily translate into the candidate being a good fit for the position and the team. If you apply to work at Cockroach Labs, you’ll be interviewed by people from different departments and through exercises. This is an unusual way to do an interview, but it works because it helps both the company and the candidate decide if they’re a good fit for the job.

Cockroach Labs has quickly established itself as one of the most promising database startups, with its distributed SQL database CockroachDB making waves in the industry. As Cockroach Labs continues to grow, competition for jobs there has intensified. This means candidates need to thoroughly prepare for the company’s rigorous interview process.

In this article, I’ll provide an overview of Cockroach Labs’ hiring process and share 15 of the most common interview questions asked. For each question, I’ll explain why it’s asked and provide a sample answer to help you craft your own winning response.

Overview of the Cockroach Labs Interview Process

The Cockroach Labs interview process is described as thorough and technically challenging, Here’s a quick rundown of what to expect

  • Initial Phone Screen A 30-45 minute call with a recruiter to evaluate basic qualifications

  • Technical Interviews: Expect 2-3 rounds of 45-60 minute interviews focused on data structures, algorithms, system design, and your specific domain expertise.

  • Take-Home Project: Some candidates are given a take-home coding assignment requiring 2-8 hours to complete.

  • Team Meetings: Final round interviews involve meeting with the team you’d be working with.

Cockroach Labs openly shares details of the process on their careers page, which candidates appreciate. However, some have noted inconsistencies in communication/feedback after on-site interviews. Overall, the process is seen as fair but demanding. Thorough technical preparation is a must.

Now let’s get into the 15 most frequently asked interview questions:

1. Walk me through your experience designing and building distributed systems.

This common system design interview question assesses your hands-on expertise in distributed systems – a key skillset needed for CockroachDB. Interviewers want to understand how you approach designing complex distributed architectures that are scalable and fault-tolerant.


In my previous role, I spearheaded the design and development of a large-scale distributed analytics system for processing millions of concurrent user events in real-time. To meet the high availability and low latency requirements, I proposed a shared-nothing cluster architecture using DynamoDB for the underlying datastore. This enabled horizontal scaling by partitioning data across hundreds of nodes.

For high throughput, the system was designed to use scatter/gather parallelism to distribute map/reduce workloads across the cluster. I incorporated redundancy by replicating partitions and load balancing reads/writes. To minimize disruptions from node failures, I built in failure detection using heartbeats and fast failover leveraging ZooKeeper for leader election.

Extensive stress testing and fault injection experiments were conducted during development to validate the system could handle node outages and traffic spikes without noticeable degradation in performance. The resulting system could easily scale out to handle a 10x increase in data volume and traffic. This experience demonstrated my ability to build distributed systems that meet strict scalability, availability and performance goals.

2. How would you detect and troubleshoot problems in a distributed database like CockroachDB?

Since outages are unacceptable for mission-critical databases like CockroachDB, you must demonstrate strong monitoring, troubleshooting and root cause analysis skills. Interviewers want to assess your ability to quickly detect, diagnose and resolve issues in complex distributed systems.


My approach would be to first leverage CockroachDB’s built-in admin UI and monitoring tools like cockroach nodestatus to identify warning signs like node liveness issues or unusual replication latency.

I would investigate further by examining metrics like SQL queries per second and service latency percentiles to pinpoint abnormal resource usage or traffic patterns. I would aggregate logs across nodes and filter for errors to identify common failure points.

Once I’ve identified a problematic component, I would reproduce the issue in a staging environment and use telemetry data to perform causality analysis – correlating events preceding and following incidents to determine root cause.

For instance, if timeline analysis showed a sudden traffic surge preceded a set of write latency spikes and node crashes, I would hypothesize the root cause as resource exhaustion. I would confirm by inspecting CPU/memory metrics at the time of failure. Finding the root cause allows me to propose targeted remediations like optimizing hot query paths or adjusting capacity.

This rigorous approach to observability and diagnostics enables me to provide swift and precise resolutions to issues.

3. How would you optimize the performance of a SQL query?

Since CockroachDB is a SQL database, you’ll need strong database development skills. Interviewers will assess your understanding of query performance factors and how you troubleshoot slow queries.


First, I would run an EXPLAIN to view the query plan and examine what indexes are being used. If indexes are missing or improper, I would add indexes on relevant columns, avoiding indexes rarely used.

Next, I would check for slow aggregations or joins dragging down performance. I would optimize aggregation by pre-computing data into a separate table. For joins, I would denormalize data to reduce join complexity.

I would also analyze query runtime statistics and logs to check for high memory/IO usage. If the dataset’s too large to fit in memory, I would experiment with breaking up the query into steps with temporary tables.

Finally, I would check if materialized views could incrementally pre-compute portions of the query to optimize read performance. By following this methodical approach, I could incrementally improve performance of even the most complex SQL queries.

4. How do you handle tradeoffs between data consistency, availability and partition tolerance in distributed database systems?

You must demonstrate a strong grasp of the CAP theorem – a fundamental principle in distributed database theory. Interviewers want to know how you navigate the tradeoffs involved in balancing data consistency vs. availability during partitions.


When data is fully consistent, every read receives the most recent write. But enforcing strict consistency reduces availability during network partitions between regions. On the other end, allowing stale reads increases availability but data may not be consistent across regions.

Based on the use case, I would make the appropriate tradeoff. For a banking application, consistency is paramount – we cannot allow withdrawals based on stale data even if it reduces availability. Here I would utilize quorum-based replication and linearizable reads.

However, for a social media feed, availability takes precedence over showing fully consistent data. Stale reads are acceptable to allow uninterrupted usage during partitions. In this case, I would allow eventual consistency across regions.

By evaluating requirements around consistency, availability, latency, and tolerance for stale data, I’m able to make the right choice for each system. I would also utilize consistency tuning capabilities like transaction priors in CockroachDB to fine-tune for the optimal balance.

5. How would you improve the performance of a web application that makes heavy use of a CockroachDB database?

This question tests your understanding of database scaling and performance optimization – both key in improving slow database-driven web apps. Interviewers want to know if you can diagnose bottlenecks and apply best practices.


I would first profile database workloads to identify slow queries, and then optimize those queries by adding indexes, optimizing joins, and fine-tuning SQL performance settings.

To scale reads, I would shard data across nodes and load balance read queries. I would also cache common queries and leverage materialized views.

For scaling writes, I would partition tables by time period or tenant ID and use consistent hashing to distribute writes evenly across nodes. I would tune the cluster for better write throughput.

Finally, I would optimize connection handling by using a connection pooler like pgBouncer and enforce connection limits to avoid overloading the database.

Following database best practices around indexing, sharding, replication, caching and connection pooling enables me to build highly performant and scalable web applications powered by CockroachDB.

6. How would you migrate a legacy Oracle database to CockroachDB?

Cockroach Labs is aiming to disrupt the database market dominated by Oracle, so expect questions about migrating from traditional databases. Interviewers want to assess your experience with migrations and database compatibility considerations.


I would follow these steps to migrate from Oracle to CockroachDB:

First, I would use the ora2pg tool to convert the Oracle schema DDL to PostgreSQL compatible syntax. I would need to resolve any compatibility issues like changing NUMBER to DECIMAL.

Next, I would set up a CockroachDB cluster and replicate the Oracle database schema using the PostgreSQL DDL. I would develop ETL scripts to migrate data from Oracle tables into corresponding CockroachDB tables in batches.

A key step is comprehensive integration testing validating migrated data and queries match the Oracle database. I would also stress test the CockroachDB cluster to benchmark performance against Oracle and optimize as needed.

Finally, I would update application code to use CockroachDB drivers instead of Oracle. I would take advantage of CockroachDB features like distributed SQL joins and parallelized query execution to enhance performance.

Following this methodical migration approach helps guarantee a smooth transition from Oracle to CockroachDB with minimal disruption.

7. How do you handle deployment and rollbacks in mission-critical production environments?

Since C

At Cockroach Labs, Show beats Tell

I quickly sent in my application when I saw the AngelList job posting for a Senior Technical Writer at Cockroach Labs. As a self-professed startup enthusiast, I love working with startups trying to solve an actual real-world problem. Cockroach Labs fit the bill perfectly.

In a few short days, I received a phone call from Lindsay Grenawalt, Head of People Operations. We talked about my technical writing experience and education. The next step was an hour-long phone interview request with Jesse, the Head of Documentation. We talked about the jobs I’ve had before, how I would handle certain documentation projects, and how I learned how to communicate technically. I thoroughly enjoyed the discussion. As the next step, I was asked to complete a take-home exercise. I was asked to install CockroachDB, create a database and a table, and document a SQL statement. How interesting it was that I had to work on a real document instead of a made-up one was the exercise.

Not long after I turned in the exercise, I was asked to fly to New York for an interview in person.

The in-person interview was a writing marathon that I had never experienced in an interview process before. Since Lindsay had informed me about the process beforehand, however, I was prepared for it. In fact, Cockroach Labs will soon make its interview questions public, which will be yet another great way to get ready for the in-person interview.

The day started with an information architecture exercise with Sean (Senior Technical Writer). I had been asked to come prepared with an information architecture presentation about a topic of my choice. This worked out well for me because it let me start the day on a positive note by showing how I organize and break down information with an audience in mind. The next two interviews were technical competency interviews. The first one was a technical talk about the distributed transaction model with Spencer (CEO), and the second one was about online schema changes with David (Engineer). I was able to show how I learn difficult topics and work with technical coworkers during these discussions by asking questions and going over the main points for them to make sure I understood them. I was asked to write down the ideas after each discussion, which let me show off my basic tech writing skills. I had a lunch meeting with Kuan (Design Lead) to share information, and I worked on editing a marketing blog with Jessica (Director of Marketing). Cross-team interviews with engineering, marketing, and design are not typical for technical writing jobs, at least not in the ones I’ve seen. These interviews gave me an insight into the collaborative work culture at the company. The final interview was with Jesse, and a wrap-up session with Lindsay.

An early part of the process made me a little nervous because none of the interviewers had seen my resume. Lindsay had explained how Cockroach Labs combats unconscious bias by removing resumes from the process. I understood the motivation for not basing interviews on resumes, but it sure got me worried. After all, I was used to having my resume as tool to demonstrate my suitability for the position. But Lindsay told me that I could talk about and explain my relevant work experience during the interviews, even though the interviewers wouldn’t look at my resume first. I took her advice and discussed my work experiences with the interviewers during the entire process. In my experience, with resume-based interviews, the discussion tends to be limited to the items in the resume. At Cockroach Labs, on the other hand, the interviews weren’t based on the resume, and I was able to talk about my relevant work experience more clearly during the interviews.

I was pleasantly surprised by the “show, don’t tell” aspect of the interviews. I wasn’t asked questions like, “How would you deal with a Subject Matter Expert?” Instead, I worked with an engineer to write documentation right then and there. I wasn’t asked, “Do you think you would fit in with the company culture?” Instead, Kuan took me to lunch and told me about it himself. It was truly an unconventional, yet insightful interview process.

Learn Everything About Cockroach Labs’ Interview Process


What is CockroachDB used for?

CockroachDB is a distributed SQL database built on top of a transactional and consistent key-value store that can withstand datacenter failures. It scales horizontally, offers high availability and can be ran in a variety of environments such as Virtual machines, containers and cloud applications.

How do you answer “Tell me about yourself” in a lab interview?

You should be honest in your response, but don’t be afraid to highlight your best qualities. Sample Answer: My strengths are my attention to detail and my ability to work independently. I’m also very good at problem solving.

Who is the CEO of Cockroach Labs?

Spencer Kimball
Cockroach Labs
Known for
Computer Programming
Spencer Kimball on LinkedIn

How many people work at Cockroach Labs?

500 people work at Cockroach Labs.

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