How Trainline’s CTO stays on track with professional development

Few would swap sunny San Francisco and the innovation of Silicon Valley for a train ticketing company serving disgruntled UK commuters, but try telling that to Trainline CTO, Milena Nikolic.

A long-time Googler, who’s role as engineering director saw her lead the Google Play developer ecosystem, Nikolic was keen for something new that offered a greater sense of social purpose.

I had been at Google for so long that I stopped counting,” she says. “It was close to 13 years… and I was itching for a bit of a change.”

In a growing technology market, Nikolic waited for the right opportunity. Nothing clicked until she spoke to Trainline, the international digital rail and coach technology platform, headquartered in London.

“Everything fell in place; every box was ticked,” she says. “I really liked the mission, connecting people to places in greener, more sustainable ways.”

The first 100 days

As the new CTO tasked with setting the technical strategy, ensuring tech team delivery, and aligning product and business strategies, Nikolic had a lot on her plate for the first 100 days.

She spent time understanding the tech stack, the business challenges, and a comprehensive technology team split across infrastructure, product development, security, privacy and technical compliance.

Trainline had sound technical systems and a good level of autonomy, but Nikolic believed the team members themselves felt less empowered to move out of their comfort zone, which impacted business outcomes.

“We had engineers who were very good specialists in their field, but I think people felt less empowered to really own goals and outcomes end-to-end,” she says. “They’re all these brilliant individuals who have a lot to add beyond coding their part of the technical system. They were more stuck to their part of the technical stack, and just contributing to that.”

This reflection pushed Nikolic to make changes to how technology teams worked across the organisation, and support a new target operating model.

Driving business growth through new teams

Trainline has been a tech-enabled business since it launched in 1997, with online ticket sales available as far back as 1999. More recently, under the tutelage of former CTO Mark Holt, Trainline became a story of scale and mobility, moving to DevOps, agile principles and leveraging compute power through Amazon Web Services (AWS).

By 2018, the Trainline platform was hosting more than 80 million customer visits a month, with more than 80% coming through mobile devices. The company sold more than 204 tickets every minute.

Today, its Platform One, with 78 million visits every month across all channels, covers more than 270 rail and coach companies across 45 countries, including over 80% of rail routes in Europe.

Milena Nikolic

Such growth in scale has resulted in a steady ramp-up in resources. Despite the COVID-19 pandemic pushing the business to reach almost £250m in debt in 2021 (the firm has since recovered to achieve net ticket sales of £2.5bn and a net profit of £90m in its latest financial results), Trainline now employs around 400 engineers, data and tech specialists who work on Platform One and process over 600 system releases every week. The company has approximately 800 staff in total across the business.

Since joining a year ago, Nikolic has split teams into horizontal and vertical functions to support operational efficiency and product development.

Horizontal team members own the platforms to ensure their robustness, reliability, latency and scalability so engineers can be productive. Vertical teams, meanwhile, operate across the tech stack so teams aren’t localised to certain operating systems, orchestration or data layers. These cross-functional teams, including product support, UX and data, offer differing levels of expertise across both front and back-end infrastructure.

“Those teams have a clear mission… that they own the product or business outcome,” says Nikolic. “They have full autonomy to decide whatever they want to do… to drive that goal, that mission and move that [business] metric in the way we expect.”

Training engineers and building products

As part of reskilling teams, Nikolic has focused on building a T-shaped skillset and giving staff the opportunity to gain broader experience. For example, she says that an iOS developer could learn eCommerce, or a web developer could study back-end infrastructure.

There have been a number of vehicles to do that, from an internal ‘tech summit’ with speakers from within and outside Trainline presenting on all things tech, product and data, to a ‘culture of craft’ community that offers regular activities, such as coding dojos, workshops, hackathons and meetups. The company also provides access to the tech learning platform O’Reilly, where team members can attend live conferences, and access books and content.

The team has celebrated numerous achievements inside her first year. Nikolic says Trainline now has a robust and scalable platform capable of withstanding 10 times search traffic and transactions, while the company recently launched STicket barcode technology to reduce friction to buy and prevent fraud. It’s also launched delay notifications in France and the UK—a smart move considering a combined 600 train delays every minute, while Trainline’s new Where next? app integrates with Apple MapKit so iOS users can plan their journey without having to leave the app.

Platform One is the solid base for all tech and innovation at Trainline, with microservices and infrastructure-as-code (IaaC) both in vogue.

“Our tech stack is built on a solid foundation provided through AWS,” she says. “By utilising a variety of technologies, such as EC2, ECS, Fargate, Kinesis and RDS, Trainline is able to achieve a hyper-scale infrastructure necessary to enable us to provide our customers with a best-in-class platform.”

Getting more women in engineering

Having worked in the industry for 15 years, Nikolic remains frustrated with a leaky pipeline when it comes to women in engineering. She admits that the tech industry can still feel less inclusive to women, and this ‘societal problem’ can push women to leave the sector mid-career.

“It’s difficult, for sure,” she says, “and, having been part of this fight for 15 years, it can sometimes be disheartening, just how slow the pace of change is.”

Nikolic is, however, hopeful that the industry can improve the representation gap. She points to examples at Trainline, where the firm has introduced diverse recruitment panels and D&I targets, as well as partnerships with coding tech school ADA in Paris and Future Frontiers, a charity equipping students from disadvantaged backgrounds across 200 secondary schools in London and Edinburgh.

She believes the key to improving the numbers of women in engineering is adding more talent at the top of the pipeline, such as encouraging disadvantaged groups from school into early stage careers.

“The only sustainable way for us to prove this is break the barriers for underrepresented groups as they enter the tech world,” she says.

Trainline remains on an upward trajectory. There’s a reported international expansion on the horizon, government contracts to win and a new CDO, hired from Meta, now reporting into Nikolic. “I really want to make sure we execute well,” she says. ”If there’s anything keeping me up at night, it’s making sure the team is set up for success in the best possible way so we capitalise on these opportunities.”

CIO, Digital Transformation, IT Skills, Women in IT