10s → <1s
Query planning time on the slowest operations
Order of magnitude faster
Faster on previously slow operations after warmup
3-phase migration
Phased migration designed to protect production traffic
Company Overview
NerdWallet is a personal finance platform that helps people make smarter decisions about their money by comparing and evaluating products like credit cards, banking, mortgages, investing, and insurance. It offers tools, content, and a mobile app to help consumers understand options, choose financial products, and track their finances with greater confidence.
The Challenge
A Gateway Architecture Under Pressure
Before switching to WunderGraph, SoundCloud relied on another federated gateway. It covered the basics, but going deeper into its features would have tied them more closely to that system than they wanted.
Upgrading was blocked.
Legacy code tied the team to an old Federation version. New subgraphs followed current Apollo patterns, but the gateway couldn't validate or plan those shapes. Teams building subgraphs found themselves constrained by a router that couldn't keep up.
Query planning started blocking traffic.
Complex queries took more than 10 seconds to plan. While those queries waited, other requests backed up behind them. The slowdown spread across the graph and began affecting users.
To compensate, the team wrote their own internal prewarming logic. It helped until a new slow query appeared. If that query wasn't added to the list, the performance of the entire graph could suffer.
Building it ourselves was something we talked about, but the amount of effort required to build and maintain it long term just wasn't worth it
The Solution
A Phased Migration to WunderGraph Cosmo
When NerdWallet evaluated alternatives, they focused on three things: Federation support, performance, and cost, both in infrastructure and team time. The migration also had to be safe.
They chose WunderGraph Cosmo and ran a three-phase rollout:
Match the gateway. Ensure Cosmo Router supported every feature the Apollo Gateway provided before touching traffic.
Sync schema registries. Publish schema updates to both registries simultaneously so the old gateway and Cosmo could stay aligned during testing.
Shift traffic gradually. Move production traffic from Apollo Gateway to Cosmo Router in small increments, validating at each step.
When roadblocks appeared - missing Federation features, behavior gaps tied to newer Apollo spec versions - the WunderGraph team patched them or built the missing support directly.
The WunderGraph team jumped in to patch issues and build features that unblocked our migration.
Subgraph teams retained ownership of their services and features throughout the migration. Internal QA ran regression tests at each stage. The phased approach allowed them to migrate while keeping user-facing behavior stable.
The Results
Lower Costs, Better Performance, Greater Flexibility
Cosmo produced immediate, measurable improvements:
Cache warming eliminated repeated 10+ second planning delays and brought planning latency down dramatically after warmup.
Removed fragile internal prewarming scripts that required manual updates every time a slow query was added
High confidence in Supergraph updates and horizontal scaling, with router version upgrades still handled carefullygs: $265,000
Improved visibility into slow queries and bottlenecks via Cosmo Studio and OTEL tracing
Reduced operational overhead — no more emergency prewarm list maintenance, fewer brittle workarounds around the old gateway
Our infrastructure costs went from $14,000 with our previous provider down to $9,750 with Cosmo.
The Conclusion
Cache Warmer: The Performance Breakthrough
The biggest improvement came from Cosmo's Cache Warmer.
Previously, NerdWallet's internal script tried to prewarm the worst offenders. It worked, but it required manual updates.
Cosmo Cache Warmer replaced this entirely. It automatically identifies and prewarms the most expensive query plans before serving traffic. Subsequent requests skip the planning phase completely.
"Caching query planning was a game-changer in terms of performance for us."
For some of their slowest production operations, cache warming eliminated repeated 10+ second planning delays and dramatically improved performance after warmup. Similar cold-start planning behavior was later documented publicly in WunderGraph’s Super Bowl scaling analysis, where cache warm-up reduced planning spikes from 8-15 seconds to below one second.
Improved Observability Across the Graph
As the platform grew, the team needed better visibility into what was happening inside the graph.Cosmo Studio provided traces, analytics, and schema visibility in one place. The team could see slow requests, identify complex execution paths, and quickly spot where subgraphs were struggling, turning guesswork into targeted fixes.OTEL tagging confirmed that performance stayed on par or improved through the migration. Cache-hit metrics helped tune the router after rollout.
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Frequently Asked Question
What led SoundCloud to migrate away from their previous GraphQL gateway?
SoundCloud’s third-party gateway worked initially but introduced high infrastructure costs and risk of lock-in due to enterprise-only features. They needed more flexibility and control over their GraphQL infrastructure without restrictive licensing.
How did WunderGraph Cosmo help SoundCloud reduce infrastructure costs?
Cosmo reduced CPU usage by 86%, from 600 vCPUs to 80, saving an estimated $265,000 annually. Their overall infrastructure spend dropped from ~$14,000 to ~$9,750 per month even after accounting for other infrastructure components.
What performance improvements did SoundCloud see after switching to Cosmo?
One high-traffic query related to reactions dropped in latency from 171ms to 94ms (P95). Routing became more efficient, reducing bottlenecks and improving responsiveness across views like track waveforms and comment counts.
How did SoundCloud approach the Cosmo migration process?
They ran Cosmo alongside their existing gateway to validate schema checks and measure performance. Once confident, they phased out the old gateway and fully transitioned to Cosmo Router.
Why did SoundCloud prefer an open-source federation router?
Cosmo’s open-source model gave SoundCloud full control without enterprise restrictions. They could inspect the codebase, avoid vendor lock-in, and maintain flexibility in how they manage their GraphQL architecture.
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