Quizlet Shares Lessons Learned from Cloud Migration Success

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Case Study

Quizlet®is a global learning platform that used VividCortex to help reduce workload on its team – saving the equivalent of 1 FT engineer – and accelerate resolution of performance inconsistencies, e.g. eliminating a 150-sec daily spike in replication lag.  

Quizlet is a global learning platform providing engaging study tools to help people practice and master whatever they’re learning. Every month,  over 50 million active learners from 130 countries use this mobile and web-based learning platform to study 400+ million sets of educational content on countless subjects. To optimize service and continue driving innovation, the Quizlet team determined they needed to take their use of cloud technology to another level by migrating from self-hosted MySQL® to Google® Cloud’s Cloud SQL.

Visibility Is the Answer

”There were definitely tradeoffs,” said Matt Lanier, Senior Director of Technical Infrastructure at Quizlet. “At the start, we had concerns, and our risk analysis showed that it was better to move ahead, even as we approached our busy season. We felt confident we could ensure strong performance because we had the full visibility into our databases that we needed to check our progress each step of the way.” 

Lanier joined Quizlet in 2018 and VividCortex database monitoring was one of the first tools he purchased – saying it was a “slam dunk” based on its proven performance. Quizlet engineers immediately began using VividCortex on a daily basis. Andrew Sutherland, the company’s Founder/CTO, led the way – routinely identifying queries that didn’t work as intended and sending links to the team so they could be improved.

Quizlet engineers followed a phased strategy for cloud migration in order to minimize potential disruption to business. For each of their 11 databases, Quizlet’s team evaluated the traffic pattern in MySQL and analyzed what the equivalent Cloud SQL instance would look like. Then they brought up that Cloud SQL instance, replicated the data to it (which sometimes took weeks) and slowly turned up read transactions to the Cloud SQL instance – using VividCortex to see how it was performing. Once they felt confident the cloud-hosted database was meeting their requirements, they would take the plunge, writing directly to the Cloud SQL instances and replicating back to the MySQL instances.

Measurable Results

Having used VividCortex to monitor database performance before, during, and after its cloud migration – Quizlet has already achieved a variety of benefits including:

  • Team Efficiency. Quizlet saved the equivalent of one full-time engineer’s time, keeping the project team lean and letting other engineers avoid distractions.
  • System Performance. One unexpected result has been a dramatic reduction of up to 50x in the standard deviation of write latency.
  • Reliability. Quizlet’s ultimate measure of the migration’s success is reliability. Moving to the cloud gives the company’s educational platform the assurance of Google’s massive redundancy and services.  

"Today, Quizlet has completed its migration to Cloud SQL. We’ve realized all our expected gains from the move including read performance, reliability and toil reduction. And we’ve garnered unexpected benefits in terms of cost reduction and increased predictability of write latency. So I’m happy to say that our cloud migration project is a success – and VividCortex played an essential role in making it happen.”"

— Matt Lanier, Senior Director of Technical Infrastructure, Quizlet

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