Introduction
Seidensticker is a long-established German fashion brand that has stood for high-quality shirts, blouses, and apparel for generations. Through its own online shop, seidensticker.com, the company reaches thousands of customers every day who navigate an extensive product range across numerous category and product pages.
For a fashion shop of this size, the speed of the category pages is decisive: this is where customers decide whether to browse the range or bounce. Slow load times on image-heavy overview pages translate directly into friction in the purchase journey.
To meet these expectations, Seidensticker adopted Speed Kit — with the goal of accelerating page delivery and making the shopping experience noticeably smoother, without any changes to the existing tech stack.
"Speed isn’t a technical detail for our shop — it’s part of the brand experience. Speed Kit made our category pages noticeably faster, and the A/B test proves in black and white that this translates directly into more conversions and revenue. The integration was seamless, with no changes to our existing stack."
Challenge
With a growing product range and a high share of image-heavy category pages, Seidensticker set out to noticeably improve the load times of these central navigation surfaces — without changes to the existing shop architecture and without additional development effort.
Solution
Speed Kit was integrated as a lightweight optimization layer — with no changes to the existing shop architecture. Its core mechanism, predictive preloading, anticipates the pages users are most likely to visit next and silently preloads them in the background. A large share of subsequent pages is therefore served straight from cache or fully pre-rendered in the background.
The result is a markedly faster browsing experience — particularly when moving between category and product pages, where speed determines dwell time and conversion.
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.
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Click the image to open the architectual diagram of Speed Kit with AWS
Results
Predictive Preloading Coverage
Performance Improvements - Largest Contentful Paints (LCP)
During the Proof of Concept (March 18 – April 14, 2026), Speed Kit delivered substantial LCP improvements — strongest on the category pages, the shop’s central navigation surfaces.
Business Impact - A/B Test: Conversion Rate Analysis
Speed Kit was deployed in a controlled 50/50 A/B test over four weeks: a Speed Kit-accelerated group was compared directly against an unaccelerated control group. Only the relative uplifts between the two groups are reported — no absolute revenue figures.
User conversion rate: +2.86% (relative)
Transactions / orders: +3.05% (relative)
Revenue: +2.66% (relative, between groups)
Statistical significance: The +2.86% relative uplift in user conversion rate is statistically significant at a 90% confidence level (p ≈ 7.74%), based on a four-week 50/50 A/B test. The improvement is not attributable to random variation.
Conclusion
For Seidensticker, performance feeds directly into the bottom line. By accelerating Largest Contentful Paint on the decisive category pages by 359 ms (~39%) and preloading a large share of subsequent pages, browsing through the range becomes noticeably smoother.
The commercial impact is clearly proven in the controlled A/B test: a +2.86% relative uplift in user conversion rate and a +2.66% relative revenue uplift versus the control group — statistically significant at a 90% confidence level.
Speed Kit is now a permanent part of Seidensticker’s performance stack, ensuring every visitor benefits from a faster, seamless shopping experience.
