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About me

Karun Thankachan is a Senior Data Scientist specializing in Recommender Systems and Information Retrieval. He has worked across the E-Commerce, FinTech, PXT, and EdTech industries. He has several published papers and holds two patents in Machine Learning. Currently, he works at Walmart E-Commerce, improving item selection and availability. Karun also serves on the editorial board for IJDKP and JDS and is a Data Science Mentor on Topmate. He was awarded the Top 50 Topmate Creator Award in North America (2024), Top 10 Data Mentor in the USA (2025), and is a Perplexity Business Fellow. He also writes to 65K+ followers on LinkedIn and co-founded BuildML, a community that runs weekly research paper discussions and monthly project development cohorts.

Frequently asked questions

How do I start a data science career with no experience?

Anyone figuring out how to start a data science career from scratch should follow the same sequence: build the non-negotiable foundations (Python, SQL, statistics, and core machine learning), then prove them with two or three end-to-end projects on real datasets rather than tutorial re-runs. Document each project like a case study — problem, approach, trade-offs, measurable result — add it to your resume, and start applying to analyst or junior data science roles. Getting your resume and projects reviewed by someone already working in the field shortens the path considerably, because self-taught candidates usually stall on blind spots they cannot see.

What is a data science career path, and how does it usually progress?

A typical data science career path runs from associate or junior data scientist, to data scientist, to senior data scientist, and then branches into staff/principal technical roles, ML engineering, research, or people management. Many people enter through adjacent roles like data analyst or data engineer and move into data science internally. Progression depends less on years of experience and more on demonstrated impact — models shipped, experiments that moved business metrics, and the trust you build with stakeholders.

Is the data science career outlook still strong with AI advancing so fast?

The data science career outlook remains strong, though the bar has risen. Companies in e-commerce, fintech, healthcare, and tech still need people who can frame the right business problem, design experiments, validate models, and turn results into decisions — work that AI tools support but do not own. What has changed is the hiring bar: employers now expect hands-on project experience, solid SQL and ML fundamentals, and clear communication. Candidates with only certificates struggle, while those who can demonstrate real impact continue to land roles.

What is a data science job actually like day to day?

A data science job is usually a mix of writing SQL to pull and sanity-check data, cleaning and exploring datasets, building or tuning models, running A/B tests, and presenting findings to product and business teams. A meaningful share of the week goes into understanding the problem and communicating results rather than modeling. The flavor varies widely by industry — e-commerce teams often work on search ranking and recommendations, while fintech teams focus on risk and fraud — which is why it is worth researching the day-to-day reality of your target industry before committing.

How to ace a data science interview?

People who ace a data science interview prepare across five fronts: SQL and data manipulation, statistics and probability, machine learning fundamentals (bias-variance, overfitting, evaluation metrics), case or product-sense questions that connect models to business outcomes, and behavioral answers built around two or three strong project stories. Drill SQL regularly, practice explaining every decision in your projects out loud, and run at least a couple of mock interviews under real time pressure — most candidates know the material but lose offers to unstructured communication.

What are data science interview questions usually focused on?

Data science interview questions cluster into six buckets: statistics (hypothesis testing, p-values, distributions), ML theory (overfitting, regularization, precision-recall trade-offs), SQL (joins, window functions), Python coding, case studies ("how would you measure the success of this feature?"), and deep-dives into your own projects where interviewers probe every choice you made. Behavioral questions round out most loops. The weighting shifts with seniority and company type — product-led teams ask more case questions, while ML-heavy teams probe theory and modeling depth.

How long should data science interview prep take?

Serious data science interview prep takes most working candidates eight to twelve weeks. A practical split: spend the first two weeks diagnosing gaps with a practice test, the middle stretch drilling your weakest areas (usually SQL or case structure) while revising ML theory, and the final two weeks on mock interviews and polishing your project stories. Cramming rarely works for data science interviews because case questions reward structured thinking that only develops through repeated practice.

What should a data science resume look like?

A strong data science resume is one page (two only with significant experience), single-column, and ATS-friendly. The structure: a short summary, a skills section listing languages, libraries, and tools, professional experience written as quantified impact bullets ("built X using Y, resulting in Z% improvement"), a projects section with links, then education. Every bullet should follow an action-method-result pattern with numbers wherever possible, and the resume should mirror keywords from each job description — most applications are filtered by software before a recruiter ever reads them.

How to make a data science resume when you have no data science work experience?

When working out how to make a data science resume without industry experience, put projects above work history and write each one like a case study: the problem, the dataset, the methods, the measurable outcome, and a link to your code. Reframe your current role in data language — reporting becomes analysis, automation becomes engineering, forecasting becomes modeling — and mirror the keywords in your target job descriptions. Two substantial, well-documented projects beat a long list of completed courses.

How to put data science projects on a resume so they actually get noticed?

The most effective way to put data science projects on a resume is to format each as a mini case study: one line of business context, the tools and techniques used, and a quantified result such as improved accuracy, reduced processing time, or influenced revenue, plus a link to GitHub or a live demo. Choose depth over volume — two or three end-to-end projects that solve realistic problems outperform a dozen tutorial clones, and the project closest to the target company's domain should sit at the top.

How to improve a data science resume that isn't getting callbacks?

To improve a data science resume that is not converting, fix the usual culprits: bullets that describe responsibilities instead of measurable impact, missing keywords from the job description (which gets you filtered out by ATS), a generic or buried skills section, and project descriptions without outcomes. Rewrite every bullet with an action, a method, and a number, tailor the resume to each posting, and cut anything that does not support the target role. If tailored applications still fail after several weeks, get an external review — you are usually blind to your own resume's weaknesses.

Do I need a master's degree to become a data scientist?

No — plenty of data scientists are hired with a bachelor's degree plus a strong portfolio, especially for analytics-facing and product roles. A master's adds the most value for research-oriented positions, for career switchers who want structured learning and recruiting access, and at teams that screen heavily on credentials. If you do apply, admissions committees weigh your statement of purpose, projects, and quantitative background heavily — a vague, generic SOP is one of the most common reasons technically strong applicants get rejected.

Is a data science career coach worth it?

A data science career coach is worth it when you are stuck: switching from another field, sending tailored applications with no callbacks, or repeatedly reaching late interview rounds without offers. What you are really paying for is outside perspective — an experienced practitioner can spot resume gaps, interview weak spots, and roadmap mistakes in one session that might take you months to diagnose alone. Vet for genuine industry experience and specific, personalized feedback rather than recycled course advice; if you are disciplined and have access to honest feedback, structured self-study can also work.

How do I build a data science portfolio that impresses hiring managers?

A portfolio that impresses has two to three end-to-end projects solving realistic business problems — not Kaggle tutorial re-runs. Each project needs a clear write-up covering the problem, data decisions, modeling trade-offs, and measurable results, along with clean, runnable code and ideally a live demo. Align at least one project with the domain you are targeting, such as a recommender system for e-commerce roles or churn modeling for subscription businesses. Reviewers spend minutes, not hours, so depth, clarity, and relevance matter far more than project count.

How long does it take to become a data scientist?

For most career switchers studying consistently alongside a job, becoming a data scientist takes roughly 12 to 24 months; those who already program or come from a quantitative field often compress that to 6 to 12 months. The timeline depends far more on how you learn than how long: focused fundamentals first, real portfolio projects second, targeted interview prep third. The most common delay is spending months collecting certificates without ever building and shipping projects, because employers hire demonstrated skill, not coursework.