Case study · Wakacje.plTravel marketplace
Feb 2026 to nowEmbedded senior frontend engineering01 / 04
Feb 2026 to nowEmbedded senior frontend engineering01 / 04
All clients
Wakacje.pl
Cutting a travel platform's bundle by 72% without freezing feature work
Performance, release reliability and accessibility fixes on Poland's largest holiday marketplace, shipped while feature delivery continued.
Travel marketplaceFeb 2026 to now
−72%
Client bundle
1.8 MB → 500 KB
What changedMeasured before
and after6 outcomes
in production02
and after6 outcomes
in production02
What changed
(01)−72%Client bundle1.8 MB → 500 KB
(02)−44%First contentful paint1.6 s → 0.9 s
(03)+62%E2E tests passing63 → 102 of 108
(04)−38%Daily Sentry incidents~800 → ~500
(05)−55%Cold build time180 s → 80 s
(06)−36%Warm build timeNext.js compiler
The processWhat we walked into
and what we didEmbedded senior frontend engineering03
and what we didEmbedded senior frontend engineering03
What we
walked into
- The client bundle had grown to 1.8 MB because two copies of the internal design system shipped together with duplicated Node dependencies.
- Every page load serialised the full promotions dictionary to the browser.
- Roughly 1.5% of requests failed on network errors and 5xx with no retry path. The E2E suite sat at 63 of 108 and Sentry logged ~800 incidents a day.
- Version skew between deploys broke 10 to 15% of monthly releases, and a Sentry/webpack race cost 2 to 3 testing days every cycle.
- Search popups trapped focus and announced nothing to screen readers.
What we
did
- (01)Audited the bundle package by package, removed the duplicated design-system copies and deduplicated Node dependencies across workspaces.
- (02)Moved the promotions dictionary behind SSR so it never reaches the client.
- (03)Designed and shipped a request-retry layer with backoff for network and 5xx failures, then reran the E2E suite as the acceptance gate.
- (04)Traced the release failures to version skew and introduced version pinning between build and runtime; isolated and fixed the Sentry/webpack race.
- (05)Migrated Babel preprocessing to the Next.js compiler and measured cold and warm builds before and after.
- (06)Rewrote focus handling and ARIA labelling in search popups, and led the above-the-fold A/B redesign on the internal design system.
StackNext.jsReactTypeScriptReact QueryMobXViteststyled-componentsLighthouse CLI
Now an agentThis playbook runs
on every commit5 agents
in the fleet04
on every commit5 agents
in the fleet04
What we did by hand,
the fleet now repeats
The agents below now run the checks, measurements and fixes from this engagement on every repository they connect to.
Next stepGains Audit
Fixed price, fixed scopeTwo weeks
One repository05
Fixed price, fixed scopeTwo weeks
One repository05
Find out what
slow costs you.
Start with a two‑week audit.
We connect the fleet to one repository for two weeks. You get a ranked list of gains in euros and the first pull requests, already open.