Specific anti-patterns to watch for during vendor evaluation. Written by a Hanoi-based founder who's also lost work to clients who got burned by the wrong vendor first. No vendor names — just patterns.
Vietnam outsourcing has a strong reputation overall — competent engineers, fair prices, decent English at the senior level. But the market is fragmented: roughly 500 vendors with ≥50 staff, and quality variance is significant. The good vendors are very good. The bad vendors look identical on the surface and only reveal themselves once you've signed.
This is the list of red flags we see most often when we get called in to rescue a project that started somewhere else. Use it during vendor evaluation to filter at the front of the funnel — before the contract is signed, when leaving is easy.
Senior Vietnam engineers in 2026 cost USD 35-60/hour at the contract level (vendor rate, not engineer salary). A vendor quoting USD 15-20/hour for "senior" engineers is staffing the project with juniors, or paying engineers below livable wages (high turnover risk), or both. Low-cost trap: the project starts cheap, then change orders + rework + missed deadlines double the real cost. The mid-market US/EU offshore budget is USD 40-80/hour for Vietnam — if the quote is half that, ask what's being cut.
Honest vendors will share the LinkedIn profiles of the 3-5 senior engineers proposed for your project before contract signing. Vendors who refuse — citing "engineer privacy" or "team allocation flexibility" — are reserving the right to swap your seniors out post-signing. The actual engineers who show up to your first sprint may be different from the ones in the sales pitch.
This clause is how vendors lock you in. Anything they build that they classify as "reusable" stays theirs; you license it back. In practice, vendors interpret "reusable" generously — your business logic, your API integrations, even your custom-trained models can be classified this way. Push for full code ownership with no carve-outs, or specifically enumerated and narrow exceptions.
ISO 9001:2015 (Quality Management) is baseline. ISO 27001 (Information Security) is mandatory for handling enterprise client data. Vendors operating without these aren't necessarily bad engineers, but they're operating without the process discipline that ISO audits enforce. Check the certificate number on the certifier's registry — several Vietnam vendors have advertised expired or fabricated certificates.
If you're a foreign company contracting a Vietnam vendor, the contract should be governed by your jurisdiction or Singapore law (via the vendor's Singapore entity). Vietnam-law contracts protect Vietnamese vendors disproportionately. "Our standard contract is Vietnam-law" is not your problem to accommodate — push for Singapore-law via their Singapore entity, and verify the entity exists at ACRA before signing.
Most "24/7 support" in Vietnam outsourcing means a junior engineer on rotating shift, who escalates to senior engineers when those seniors are awake. The result: in your first emergency, your ticket sits with a junior for 6-8 hours before a senior touches it. Demand specifics: which named senior engineers are reachable in which hours, and what's the escalation path.
Time-and-materials billing aligns vendor incentives toward longer projects. Fixed-fee billing forces the vendor to estimate, commit, and own scope. Vendors that exclusively quote T&M are either (a) unwilling to commit to estimates, which signals they don't have confidence in their own delivery, or (b) intentionally avoiding accountability. Fixed-fee should be available for any well-scoped project of less than 6 months.
Engineering practice moves fast, especially in AI/ML. A vendor showcasing 2022-2023 wins as their headline work is either not shipping recent client wins (red flag), or their best clients have NDAs preventing publication (which is normal — but then ask for non-public references). Modal good signal: 5+ case studies from the last 18 months, with named clients or verifiable industry + scale.
Common pattern: the founder or CTO joins the sales discovery call, then disappears once contract is signed. The project lead becomes a junior PM you've never met. This is okay if the vendor is large enough that the founder genuinely can't be on every project, but it should be explicit: "For this project, your day-to-day will be X (senior PM) and Y (tech lead) — both senior, both with profiles I'm sharing now." If post-sale team is opaque during sales, expect downgrade.
For AI/ML specifically: vendors that can't explain their evaluation methodology in 90 seconds are not actually shipping AI in production. "We test thoroughly" or "the model worked well in our tests" is a fail. The right answer mentions a frozen eval set, scoring functions per task type, CI-gated regressions, and component-level evals (retrieval vs generation vs reasoning). Without an eval framework, the AI they ship will rot inside 6 months and they won't notice.
For balance — the inverse of the red flags above is what you actually want to see. A healthy vendor:
Free 30-minute call: bring your vendor's deliverables, status reports, or contract clauses. We'll tell you honestly whether the red flags add up to a structural issue or are individually fixable. Even if the answer is "keep working with them, here's what to push on," the call is free and confidential.
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