Introduction
Kastner & Öhler is one of Austria's most iconic fashion retailers, with roots going back to 1873. Operating premium department stores across Austria and Germany, including the landmark flagship in Graz.
The group serves a broad fashion-conscious audience under both the Kastner & Öhler and Gigasport banners. The brand stands for quality, style, and a shopping experience that is equal parts aspirational and accessible.
With a strong and growing online presence, the group's digital channels have become a central pillar of its commercial strategy. For a retailer whose in-store experience is outstanding, the online shop needed to match those same standards of excellence, which meant page speed could not be an afterthought.
"Speed Kit delivered exactly what was promised, a measurably faster experience for our customers with no disruption to our operations. The results from the proof of concept were compelling enough to move forward with confidence."
Challenge
Matching the in-store experience online
As the fashion retail landscape shifts further toward digital, kastner-oehler.de has evolved into a primary touchpoint for both acquiring new customers and deepening loyalty with existing ones. Yet performance data revealed a significant gap: server response times (TTFB) were elevated across all page types — particularly on category and product pages, which are the most critical pages in the purchase funnel.
For a brand that prides itself on an exceptional customer experience, slow-loading pages represent a real contradiction. Every additional second of load time risks abandoning the promise that Kastner & Öhler has built over 150 years. The challenge was clear: close the performance gap quickly, without a lengthy re-platforming project, and deliver results that show up directly in the business numbers.
Solution
Speed Kit — near-instant pages across the entire storefront
Kastner & Öhler operates a high-traffic fashion e-commerce platform on kastner-oehler.de, serving a broad audience across Germany. Speed Kit was integrated to deliver a single, low-friction acceleration layer across all page types simultaneously, from homepage to category listings to product detail pages.
Speed Kit works by intelligently caching dynamic content and proactively preloading the most likely next pages in the customer journey, moving content from the server to the browser before the user even clicks. The result: page transitions that feel near-instant, on both desktop and mobile.
The Largest Contentful Paint (LCP), Google's core metric for page load experience and a direct signal for search rankings, improved substantially across all page types on kastner-oehler.de, with the strongest gains on category pages.
Speed Kit is an official ACE eligible technology partner and independent software vendor (advanced tier) of the AWS Competency Partner Program "Accelerate" as well as the Workload Migration Program. Our technology is powered by 13 different AWS services:
- Elastic Kubernetes Service (EKS): We use EKS to schedule and orchestrate our Speed Kit applications on EC2 instances.
- Simple Storage Service (S3): Speed Kit stores cached assets in S3 buckets. Additionally, we store RUM (Real User Monitoring) and PI (Performance Insights) data in S3 buckets for analytics purposes.
- Elastic Compute Cloud (EC2): Our workloads are hosted on EC2 instances, as managed through EKS.
- Kinesis Data Streams: Kinesis Data Streams are used to ingest RUM and PI data from Speed Kit, which is then consumed by Amazon Managed Service for Apache Flink. Fastly also streams access logs to our Kinesis Data Stream, which are similarly consumed by Amazon Managed Service for Apache Flink.
- Athena: We use Amazon Athena to query data stored in AWS S3 buckets, enabling performance insights and asset preloading.
- Elastic Container Registry (ECR): Docker images are stored in ECR and deployed in our Kubernetes cluster, which is managed by EKS. For third-party application images, we use the pull-through-cache feature of ECR.
- Elastic Container Service (ECS): We build Docker images using a service hosted on Amazon ECS.
- Route 53: Route53 is used to manage DNS records.
- Simple Email Service (SES): We use SES is used for sending transactional emails.
- Managed Streaming for Apache Kafka (MSK): We use MSK to facilitate consuming and producing custom event records for different applications.
- DynamoDB: Speed Kit uses DynamoDB to store information related to our predictive preload feature.
- Lambda: We use Lambda to pre-render client side renderd pages to make that actual server side rendered.
- ElastiCache (Redis OSS): We use ElastiCache to store our Bloom filter, which checks whether an asset is present in our cache.
-min.webp)
Click the image to open the architectual diagram of Speed Kit with AWS
Results
Speed Kit performance uplift
Results are based on Speed Kit RUM data collected during the proof-of-concept period for kastner-oehler.at.
Enabled Pages: 1,428 ms → 728 ms = −700 ms = 49% faster
Product Pages: 1,288 ms → 604 ms = −684 ms = 53% faster
Category Pages: 954 ms → 559 ms = −395 ms = 41% faster
Conversion rate uplift
Speed Kit was deployed in an A/B test, delivering a measurable and direct impact with a +3.47% conversion rate uplift, confirming that faster page loads translate directly into more completed purchases.
A performance foundation for continued growth
For Kastner & Öhler, Speed Kit is not just a technical optimization; it is a direct expression of the brand's core commitment to service quality. A brand that has spent over 150 years building trust through exceptional in-store experiences cannot afford to offer a digital journey that feels slow or unresponsive.
With a statistically significant +3.47% uplift in conversion rate and LCP improvements of up to 49% on category pages, the proof of concept has made a compelling case for a full rollout across all storefronts and markets.
Speed Kit is positioned as a long-term performance partner for the Kastner & Öhler group, ensuring that the quality customers experience in-store is felt from the very first click.
