Technical audits: Optimizing cost, performance, and productivity

Every 100ms of latency can cost ecommerce applications up to 8% in sales conversion. At scale, this can cost millions in revenue.

Complexity compounds as applications grow, making these performance issues harder to diagnose and fix. Audits help teams navigate these challenges systematically.

This article covers strategies we've developed across hundreds of real-world audits.

The tipping point: When performance meets scale

Recently, one of our enterprise ecommerce customers hit a common inflection point.

Their Next.js application launched with great performance metrics, but as they added personalization features to drive engagement, complexity grew. Simple A/B testing evolved into sophisticated user recommendations and dynamic pricing, which hurt their metrics.

The impact was immediate and severe:

• Time to First Byte (TTFB) jumped 300%

• Conversions dropped 15%

• Server costs doubled in three months

The issue wasn't technical debt or poor architecture. It was the inherent challenge of balancing static optimization with dynamic features.

Through our technical audit, we helped them keep their new features while restoring performance. This resulted in cutting TTFB by 70%, returning conversions to previous levels, and reducing server costs by 40%. Most importantly, we helped them establish patterns to maintain performance while adding new dynamic features.

Technical audits deliver the most value at specific inflection points in your application's lifecycle. Let's explore how you can identify these opportunities.

Three types of technical audits

1. Code Review Audits: When architecture needs validation

Code Review Audits help you optimize rendering and caching strategies during major transitions. When a large ecommerce platform needed to migrate from Pages Router to App Router, we helped them identify optimization opportunities:

• React Server Components (RSC) payloads that were 3x larger than necessary

• Data fetching waterfalls impacting page performance

• Suboptimal caching strategies affecting performance

Our comprehensive analysis delivered:

• Code and framework best practices

• Framework-optimized code examples, patterns, and strategies

• Prioritized and detailed action plan

• A detailed migration roadmap with milestones

After following our action plan, they completed their migration 40% faster than estimated while improving key performance metrics.

2. Web Performance Audits: When performance impacts revenue

A major retailer approached us with a problem: their conversion rates were dropping fast. While their initial analysis suggested performance issues, pinpointing the exact cause proved challenging. Our Web Performance Audit revealed three performance issues:

• Third-party scripts degrading Core Web Vitals

• Poor image optimization causing slow Largest Contentful Paint (LCP)

• An inefficient API waterfall in key user flows

By addressing these issues head-on, we helped them get back on track:

• 45% faster Time to Interactive (TTI)

• 6% higher conversion rates

• Improved Core Web Vitals across the board

Web Performance Audits are most valuable when evaluating site performance before launches, during any framework migrations, and for measuring real-world user experience.

3. Usage Audits: When scale drives costs

What works for thousands of users can break down at millions. We saw this firsthand when an enterprise customer's serverless costs increased dramatically due to inefficient async operations. Our Usage Audit pinpointed three issues:

• Async waterfalls in product and category data fetching causing redundant serverless executions

• Static pages regenerating too frequently due to short Incremental Static Regeneration (ISR) times

• Inefficient data caching patterns causing unnecessary API calls

By implementing targeted optimizations based on real usage data, they reduced their infrastructure costs:

• Serverless function executions dropped by 60% through parallel data fetching

• Cache hit rates improved by extending ISR times and implementing on-demand revalidation

• API calls reduced by 40% through optimized caching strategies

Usage Audits help you optimize infrastructure before costs spiral. You get clear data about how your application consumes resources, letting you make informed optimization decisions. Most importantly, they help establish patterns that maintain performance while adding new features.

A diagnostic-first approach

Effective technical audits begin by analyzing the gap between intended goals and actual production performance, rather than starting with code review. We assess:

• User experience: The application's real-world performance, identify friction points in user flows, and pinpoint where performance metrics start to degrade

• Resource efficiency: How effectively the app uses platform resources, uncovers areas driving unexpected costs, and identifies usage patterns that need optimization

• Development velocity: Deployment frequency and identify developer roadblocks that add friction to delivery

This analysis often surfaces key issues impacting application performance and developer productivity.

• Performance bottlenecks: High TTFB, slow navigations/interactions, and redundant resource preloads

• Resource waste: Overactive page generations, bandwidth spikes from unoptimized images, unoptimized RSC payloads, and inefficient Edge Middleware patterns

• Developer friction: Misunderstanding of React and Next.js best practices, slow build times, and unintentional security oversights

This diagnostic-first approach ensures we target improvements that deliver the most value. Understanding the impact on business goals helps prioritize fixes effectively.

Common patterns that impact performance

After conducting hundreds of technical audits, we've identified key patterns that consistently affect applications. Let's explore some of the most impactful ones and their solutions.

Dynamic features vs. static optimization

Teams often achieve great initial performance through static optimization, only to see it degrade as they add dynamic features. This pattern emerges frequently in ecommerce, where personalization, A/B testing, and inaccurate data directly impact revenue.

Negative business impact:

• Misaligned rendering strategies, such as using server-side rendering (SSR) where static would suffice or missing SSR on dynamic paths

• Lower conversions from slower page loads

• Degraded user experience from increased TTFB

Common implementation issues:

• Static optimization disabled across entire routes

• Page-level data fetches that block rendering

• Client-side A/B testing impacting performance

Recommended solutions:

• Use Edge Middleware with ISR for auth flows

• Push data fetching down to the component level, often with SWR

• Move A/B testing to the server using Edge Middleware for pre-computed variants

Typical outcomes:

• 40-60% reduction in server costs

• Return to baseline conversion rates

• Significant TTFB improvements across global regions

Resource optimization

As applications scale, resource usage patterns become increasingly important. We consistently see this with serverless functions and third-party integrations, where small inefficiencies compound into significant costs.

Negative business impact:

• Increased bandwidth costs from inefficient CDN configurations

• Higher serverless costs that grow exponentially with increased traffic

• Degraded performance in global markets

Common implementation issues:

• Unoptimized images creating larger page size

• Images missing width and height attributes causing layout shift

• Autoplay videos loading on page load, often from the public folder

• Sequential API calls instead of parallel API calls in serverless functions

• Using an additional CDN in front of Vercel's already-optimized Edge Network

• Inefficient authentication patterns in middleware affecting all traffic

• Dynamic routes without cache control

• Inconsistent data fetching patterns across components, which can lead to redundant requests and increased load times

Recommended solutions:

• Define image dimensions and use optimized image formats, which Next.js's Image component can help enforce and serve automatically

• Load video content via blob storage or CDN with lazy loading and/or chunked streaming

• Establish consistent and parallel data fetching patterns

• Implement efficient authentication patterns across edge middleware, components, and API endpoints and target specific routes

• Add strategic caching to minimize function calls

Typical outcomes:

• 30-40% reduction in bandwidth usage

• 50% fewer serverless function executions

• 90% cache hit rates globally

Migrating from Pages Router to App Router

The transition to Next.js App Router unlocks powerful new capabilities, but requires careful planning and a change in patterns.

Negative business impact:

• Delayed feature delivery during extended migrations

• Higher resource costs from inefficient patterns

• Performance drops affecting user experience and revenue

Common implementation issues:

• Oversized RSC payloads sending unnecessary data to clients

• Incorrect client/server component boundaries causing excess client-side JavaScript

• Missing cache configurations in data fetching

• Props passing entire objects between server/client boundaries instead of specific fields, causing unnecessary re-rendering

• Legacy patterns, such as not relocating asynchronous functions to the server, blocking static optimization

Recommended solutions:

• Incrementally migrate from Pages Router to App Router instead of all at once (you can use both in Next.js at the same time)

• Profile RSC payload size using Chrome DevTools and minimize where possible

• Use Suspense boundaries for effective client/server rendering

• Implement granular caching with use cache, revalidatePath, and revalidateTag

• Use React.cache() and Suspense boundaries to manage complex calls more effectively

Typical outcomes:

• 40% faster migration completion

• 50% reduction in client-side JavaScript

• Improved Core Web Vitals across all metrics

Development experience improvements

Improving developer velocity means your users get new features faster and your developers can ship fixes quickly, resulting in a better experience for everyone.

Negative business impact:

• Extended build times blocking rapid iteration

• Inability to address critical issues during crucial business times (like Black Friday-Cyber Monday)

• Technical debt compounding over time

Common implementation issues:

• Unoptimized Next.js configurations causing slow builds, particularly from missing bytecode caching

• Inefficient module imports

• Trade-offs between DX and performance

• Excessive use of third-party libraries, which can weigh down local development

Recommended solutions:

• Optimize build configurations for your use case

• Avoiding barrel files for better bundle times and smaller client-side JavaScript

• Balance developer experience with performance needs

• Audit and remove any unnecessary third-party code

Typical outcomes:

• Build times cut in half

• Bundle size reduced by 33%

• Measurable increase in deployment frequency

Building sustainable patterns

Technical audits work best as catalysts for sustainable improvement, not one-time fixes. They provide value at every stage of your application's lifecycle—before, during, and after major migrations. The goal is to establish patterns that help you build better applications for the long term.

While audits can help identify optimization opportunities during migrations, comprehensive migration support is available through our additional consulting services. This includes guidance for monolith-to-headless transitions and framework migrations.

To help you implement our recommendations effectively, each audit includes four 30-minute weekly office hours sessions. During these sessions, our experts can answer questions and provide guidance on implementing audit recommendations.