Fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) improves clinical outcome compared with angiography-guided PCI. Advances in computational technology have resulted in the development of solutions, enabling fast derivation of FFR from imaging data in the catheterization laboratory. The quantitative flow ratio is currently the most validated approach to derive FFR from invasive coronary angiography, while the optical flow ratio allows faster and more automation in FFR computation from intracoronary optical coherence tomography. The use of quantitative flow ratio and optical flow ratio has the potential for swift and safe identification of lesions that require revascularization, optimization of PCI, evaluation of plaque features, and virtual planning of PCI.