In a hyper growth product company continuous evolution of systems is inevitable as technology improves everyday, product and business needs evolve regularly and change in scale impacts operating costs. At Spotify the ads systems have undergone several changes fundamentally over the years. The performance needs from Spotify's ad technology stack are very demanding - high volume, high availability and low latency. Any downtime or outage has a direct and real revenue impact. Overtime as newer consumer platforms have emerged, backend and data infrastructure technologies have matured and Spotify products have evolved; the needs of the ad technology systems have changed as well. This has resulted in continuous evolution of individual components and the overall architecture. In this talk the speaker will share his experiences about lessons learnt while evolving Spotify's Ad systems without disrupting daily activity.