When 500,000 people gather in one place, they all want the same things: the perfect photo, the flawless story, and an internet connection that doesn’t collapse under pressure. That was the focus of the latest Sofascore Stadium Meetup, held under the title Signal for Half a Million Stories.
The meetup addressed a once-in-a-generation challenge: how to keep half a million people online at the same time. The ultimate test came this July at Zagreb’s Hippodrome, where Marko Perković Thompson hosted the largest concert ever held in the region. While fans sang along, a massive backstage operation unfolded – one where all major telecom operators joined forces to build a network strong enough to handle several hundred thousand parallel connections.
Building a Network for 500,000 Stories
The panel brought together three key players: Goran Toplek, Director of Engineering for Access Networks at Hrvatski Telekom, Jadranko Dundović, Head of IT Infrastructure Coordination and Supervision for the concert, and Mirko Gudelj, the event organizer.
“We didn’t start out knowing half a million people would show up,” admitted Toplek. “The original estimates were smaller, and then came the reality check. Either our team would make it happen, or no one would. We built 37 new base stations across 11 locations, and by the end more than 90 terabytes of traffic went through the mobile networks. Instagram alone accounted for 20% of that, WhatsApp 18%, and phone calls increased by 120% compared to a normal day.”
When Backup Needs a Backup
For concert organizer Mirko Gudelj, the stakes went far beyond streaming a story. “The risk was enormous. Not financial, but safety-related. If someone can’t buy water or reach help, that’s a problem. That’s why we had backups for our backups and several parallel options ready. More than 700 people and over 100 companies worked on the project – from software and hardware to scaffolding and cranes. Everything had to be synchronized.”
Gudelj also noted that his past experience at events without reliable signal made the challenge even clearer. “I had to bring my own servers before just to keep things running. This time, the goal was simple: it all had to work.”
Infrastructure Without Compromise
Jadranko Dundović confirmed just how unforgiving the setup was. “There was no cash payment at the concert, only card transactions. It was operationally impossible for the system to fail, it had to work perfectly. The safety aspect was equally important. 250 surveillance cameras covered the entire Hippodrome, and a mobile app, with user permission, helped us optimize security checks. We also had a VAR-style control room integrating all those cameras.”
The numbers underline the scale:
- 92 km of ethernet cable
- 17 km of optical fiber (laid and re-laid)
- 30 km of piping
- 140 network switches supplied by Hrvatski Telekom
- Two aggregated fiber links, each from a different side of the Sava River, backed up by Starlink connections
“There were no shortcuts in the investment,” Dundović added. “We even faced a heavy rain just before the concert, which could have ruined equipment, but everything held. That’s when you see the importance of quality infrastructure.”
A Signal That Never Broke
Beyond the cables, antennas, and servers, there was also power – 300 kW of electricity dedicated to making sure everything ran smoothly. Even the highways leading to Zagreb were part of the plan, with network options prepared in case traffic jams stranded fans.
Priorities were set clearly:
- Civil services
- Mobile payment systems
- Everything else
This structure ensured safety, payments, and communication never stopped. Monri alone operated more than 800 cash registers and point-of-sale devices on site.
A Full House at Sofascore
The massive interest in the topic proved once again how relevant it is. Sofascore’s event space was filled to the last seat, with several hundred more following via livestream.
Watch the whole meetup here:
>> Sofascore Hosts First Regional ClickHouse Meetup: A Big Data Revolution in Zagreb
Closing the panel, Josip Stuhli, CTO at Sofascore and event moderator, summed it up perfectly: “Events like this show that technology isn’t just support – it’s the condition that makes the experience possible. If a signal can withstand half a million people, then we know we can push the boundaries even further. Sometimes the biggest success is when no one notice, because everything simply works.”
Check out the whole gallery:
