Google Search: Behind the Scenes with Site Reliability Engineers
Google Search is an essential part of life for billions of people, delivering answers and information in an instant. But the smooth operation of this massive system is no accident—it relies on the tireless efforts of Google’s Site Reliability Engineers (SREs). In a recent episode of Search Off the Record, two of Google’s SREs, Ben Walton and David Yule, shed light on their critical roles, giving listeners an inside look at how they keep Google Search reliable around the clock.
What Do SREs Do?
SREs work behind the scenes to ensure that services like Google Search remain operational under even the most challenging conditions. According to Ben, their primary goal is to make sure that “everything works smoothly because of the work you do.” While they may seem invisible when things are running well, their influence is felt when issues arise. As David explained:
“The main focus is, we’re software engineers just like the folk developing features in Search, but our focus day-to-day is working out how we can make web search that bit more reliable, that bit safer.”
A large part of their job is to prevent incidents from happening, but when they do, SREs are the first to respond. Ben highlighted that they must be deeply familiar with how systems work at the lowest levels to anticipate potential issues:
“We try to be very proactive and forward-looking, engaging on as many of the large changes as we can.”
Balancing Proactive and Reactive Work
One of the ongoing challenges for SREs is striking the right balance between proactive and reactive work. Ideally, their proactive efforts to strengthen and improve the system prevent problems from occurring, but there are always unexpected issues that need immediate attention. David pointed out:
“Aiming for 100% reliability is impossible. You’re never going to do it. You’re always going to have issues.”
SREs have to determine the right level of reliability based on the needs of different services. “For Search, obviously it’s a very high-profile service, so we keep ourselves to a very high standard,” David explained. This often means slowing down development to ensure reliability. As Ben added:
“An additional nine [in reliability] can cost an awful lot of money, in terms of resources and engineering effort.”
The Stress and Teamwork of Being On Call
One of the most intense parts of an SRE’s role is being “on call,” which means they must be ready to respond to issues at any time. “If you’re not a little bit terrified of being on call for Google Search, you’re too numb at that point,” Ben remarked, reflecting on the pressure of the role. But both Ben and David emphasized the supportive team culture that helps manage the stress.
“When you’re on call, you can be the most junior person on the team and you can get directors to go get resources for you and help fix problems,” David explained.
The SRE culture at Google is highly collaborative, ensuring that no one feels overwhelmed.
“It feels like a team sport when the big issues arise,” David added.
The World Cup Incident: A Real-Time Challenge
Perhaps one of the most memorable moments for Google’s SRE team came during the 2022 FIFA World Cup, when traffic to Google Search surged unexpectedly during key moments of matches. As David recalled:
“We got alerted and it was one of these failures which was a success failure. We suddenly got way more traffic than we were expecting.”
When users searched for player stats and match updates after every goal, the spikes in traffic were so large that they began to strain Google’s systems. While the SRE team had anticipated high traffic, this unprecedented surge pushed the system to its limits. David explained:
“My mental model before this was, if there’s a match on, you watch the TV, you watch the match. Turns out people also search, especially when there’s a goal.”
Thanks to automated alerting systems, the team caught the issue early and quickly mobilized. Ben highlighted:
“The alerting gave us a very direct signal as to where to look for issues.”
By reallocating resources and adjusting their systems, the team managed to prevent significant user impact. The SREs spent the following weeks optimizing their systems to ensure they could handle the even larger traffic spikes expected during the World Cup final.
As a result, the final ran smoothly, breaking traffic records for Google Search. Sundar Pichai, CEO of Google, later tweeted, “Search recorded its highest ever traffic in 25 years during the final of the FIFA World Cup.” David reflected on the experience:
“It was one of those outages that, in the end, had a happy ending.”
How to Become an SRE
For those interested in pursuing a career as an SRE, both Ben and David emphasized that it requires a blend of engineering skills and a problem-solving mindset. Ben noted:
“You don’t need a traditional computer science background.”
Instead, what matters most is a curiosity for understanding how systems work and an ability to troubleshoot when they don’t. “Computers always break, so there’s plenty of use cases to find out what’s going wrong and why,” David added.
Along with technical expertise, communication skills are crucial in the role, since SREs often need to collaborate with teams across the company. As David put it:
“Probably the soft skills around communication and collaboration are way more important for an SRE than your Linux skills.”
Conclusion
This episode of Search Off the Record gave listeners a rare glimpse into the life of Google’s SREs, showing just how critical their role is in keeping Search reliable for billions of users. Whether responding to sudden traffic spikes during the World Cup or preventing future incidents, SREs are the unsung heroes who ensure Google Search remains one of the most trusted and dependable services on the internet.
As Ben concisely put it:
“Every day is different. You’re solving puzzles.”
It’s this problem-solving spirit, combined with technical expertise and teamwork, that makes SREs the guardians of Google’s vast infrastructure—ensuring it continues to deliver, even under the most demanding conditions.
References:
This article is based on a YouTube video from the ‘Search Off the Record’ podcast by Google Search Central. You can watch the full episode here
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