This paper presents a Bayesian parameter estimation of the millisecond pulsar PSR J0030+0451, focusing on its mass and equatorial radius. The analysis is based on pulse-profile modeling of Neutron Star Interior Composition Explorer (NICER) X-ray spectral-timing event data, which involves relativistic ray-tracing of thermal emission from hot regions on the pulsar's surface. The study explores various configurations of these hot regions, including their shapes and temperatures, and uses the X-PSI software package for Bayesian modeling. The results indicate that both hot regions are located in the same rotational hemisphere, with one being a small circular spot and the other a narrow arc. The inferred mass and equatorial radius are $1.34^{+0.15}_{-0.16} \, \text{M}_\odot$ and $12.71^{+1.14}_{-1.14} \, \text{km}$, respectively, with a compactness of $0.156^{+0.008}_{-0.010}$. The paper also discusses the implications of these findings for understanding dense matter, pulsar emission mechanisms, and stellar evolution.This paper presents a Bayesian parameter estimation of the millisecond pulsar PSR J0030+0451, focusing on its mass and equatorial radius. The analysis is based on pulse-profile modeling of Neutron Star Interior Composition Explorer (NICER) X-ray spectral-timing event data, which involves relativistic ray-tracing of thermal emission from hot regions on the pulsar's surface. The study explores various configurations of these hot regions, including their shapes and temperatures, and uses the X-PSI software package for Bayesian modeling. The results indicate that both hot regions are located in the same rotational hemisphere, with one being a small circular spot and the other a narrow arc. The inferred mass and equatorial radius are $1.34^{+0.15}_{-0.16} \, \text{M}_\odot$ and $12.71^{+1.14}_{-1.14} \, \text{km}$, respectively, with a compactness of $0.156^{+0.008}_{-0.010}$. The paper also discusses the implications of these findings for understanding dense matter, pulsar emission mechanisms, and stellar evolution.