TypeScript Offshore Development: Skills to Vet Beyond the Job Post in 2026

Last updated: July 7, 2026

Every offshore TypeScript resume says roughly the same thing. Five years experience. React, Node, Next.js. Strict mode. None of it tells you whether the person behind it actually thinks in types, or just wraps JavaScript in .ts files and hopes the compiler stays quiet.

That gap matters more now than it did two years ago. TypeScript passed Python in August 2025 to become the most-used language on GitHub, with 2.64 million monthly contributors according to GitHub’s own Octoverse report. Everyone’s resume claims it now. Fewer engineers than you’d expect can actually defend a type design decision under pressure.

If you’re building an offshore engineering team, TypeScript talent is one of the roles worth vetting carefully before you extend an offer, because the cost of getting it wrong shows up six months later, buried in a codebase nobody wants to touch. This guide covers what to test beyond the job post: the type-system skills that separate real engineers from JavaScript developers with types bolted on, how to test for them, and the offshore-specific risks a resume will never show you.

Why a TypeScript Job Post Can’t Tell You Who’s Actually Qualified

A job post asks for TypeScript. Every candidate answers with TypeScript, because keyword matching is how offshore agencies build shortlists in the first place. That’s the whole problem. The job post is a keyword filter. It was never built to test type-system depth.

State of JS 2025 puts the average TypeScript usage share at 77% across respondents, and the largest single group, 4,367 people, now write 100% TypeScript. When adoption gets that high, “I have TypeScript experience” stops being a meaningful filter. It just means the candidate has touched a .ts file. It doesn’t mean they understand why strictNullChecks exists, or when to reach for a discriminated union instead of another optional field.

Here’s the tell most hiring managers miss. A developer who spent two years on a project with strict: false and a codebase full of any has technically “used” TypeScript for two years. So has someone who spent that same stretch designing exhaustive union types and catching bugs at compile time instead of in production. Same resume line. Completely different skill level. The job post can’t tell the two apart. You have to.

The Type-System Skills That Separate Real TypeScript Engineers From JavaScript Developers With Types Bolted On

Skip the trivia questions about interfaces versus types. What actually separates a TypeScript engineer from someone typing JavaScript with a .ts extension comes down to three things.

Generics with real constraints, not just angle brackets. Anyone can write a generic function. Ask a candidate to build one that only accepts objects with a specific shape, and watch whether they reach for an extends constraint or just remove the type entirely because it’s easier to silence the error.

Discriminated unions and exhaustiveness checks. This is the strongest senior-level signal in TypeScript hiring right now. A developer who models application state as a discriminated union, then writes a switch statement with a never check at the end, is building code that fails to compile the moment someone adds a new state and forgets to handle it. That’s a design habit most JavaScript-first developers never pick up, because JavaScript never forces the issue.

Strict-mode fluency, not just strict: true in a config file. The official strict flag bundles 9 separate checks, including strictNullChecks, noImplicitAny, and strictFunctionTypes. A candidate who can explain why strictNullChecks should land before the rest, or knows when a codebase needs noUncheckedIndexedAccess on top of the base set, has actually migrated a real project through strict mode. Someone who just says “yes, we use strict mode” usually inherited a config file someone else wrote.

How to Actually Test These Skills Before You Sign

Testing this doesn’t require a 4-hour take-home assignment. It requires looking in the right places.

Audit the GitHub history, not just the profile. A polished GitHub profile full of forked tutorial repos tells you nothing. Open a project the candidate wrote from scratch. Check the tsconfig.json. Is strict on? Is the codebase full of any used as an escape hatch, or are types applied on purpose? Real commit history, with incremental changes and real bug fixes, is a stronger signal than a single polished repo pushed in one commit.

Run a 20-minute paired exercise instead of a written test. Give the candidate a small, ambiguous data shape, an API response that can return three different states, for example, and ask them to model it live. Watch whether they reach for a discriminated union or default to a pile of optional fields and if statements. Then ask them to explain a tradeoff out loud. This is where interview fraud gets caught fastest, because a stand-in candidate can’t explain reasoning they didn’t generate.

Ask about a real strict-mode migration. Not whether they’ve “used” strict mode. Ask what broke first when they turned it on for an existing codebase, and how they prioritized the fix. strictNullChecks almost always surfaces the most errors first, so a candidate describing a very different experience is either exaggerating or was on a greenfield project with the flag on from day one. Both are fine answers. The story just needs to hold up under a follow-up question.

This layer sits on top of the broader offshore vetting framework we run for every technical hire, from the async screen through the technical assessment, live interview, and paid trial. The TypeScript-specific checks above slot into the technical assessment and live interview stages.

The Offshore-Specific Risks a Resume Never Shows You

TypeScript skill is only half the vetting problem when the hire is offshore. The other half is confirming the person you interviewed is the person who shows up on day one.

Proxy interviews are the costliest failure mode. A senior engineer handles the interview call, performs well, and a different, more junior developer gets assigned to the actual work once the contract is signed. DistantJob’s vetting research flags this as one of the most common offshore hiring failures. Ask for the resume and LinkedIn of the specific person doing the work before anything is signed, not just the person on the sales call.

Resume-dumping is a vendor red flag, not a candidate one. If an offshore partner sends 20 to 30 resumes within 48 hours of a request, they’re not vetting, they’re forwarding. Per incommon.ai’s red flag analysis, a partner that actually pre-screens will typically hand you 2 to 3 strong matches, because the filtering happened before you ever saw a name.

Async communication is a skill you can test in writing, before the interview. Send a written technical question and see how they answer. Vague, off-topic, or one-word replies in writing predict the same pattern once they’re three time zones away and a Slack message is the only way to unblock them.

Interview Questions That Screen for What a Job Post Can’t

Use these as follow-ups once a candidate clears the resume screen. Each one is built to expose the gap between “has used TypeScript” and “thinks in types.”

• Walk me through a discriminated union you’ve built and why you chose it over optional fields.
• What’s the first thing that broke when you turned on strict mode in an existing project, and how did you triage it?
• Show me a generic function you wrote with a real constraint. Why did you constrain it that way instead of leaving it open?
• Describe a type-related bug that would have been a runtime error in plain JavaScript. How did the compiler catch it instead?
• What’s in your tsconfig.json beyond strict: true, and why did you add it?

None of these have a single correct answer. What you’re listening for is whether the reasoning holds together, whether they can defend a tradeoff, and whether the story sounds like something they lived through instead of something they memorized the night before.

A TypeScript job post filters for keywords. It was never going to filter for judgment. The developers worth hiring are the ones who can explain why they modeled a type the way they did, who’ve actually broken and fixed a strict-mode migration, and who show up as the same person you interviewed once the contract is signed.

Test for that before you sign anything, not after the first sprint reveals it. If you’d rather skip the manual audit process, Kore BPO’s vetted offshore TypeScript engineers already clear these checks before you ever see a resume.