There Is No Single Quant Interview
“Quantitative finance” covers several different jobs, and interview preparation should reflect that.
A derivatives pricing quant may need deep knowledge of stochastic calculus, risk-neutral valuation, volatility models, calibration, and numerical methods.
A quantitative researcher may be tested more heavily on probability, statistics, time series, experimental design, machine learning, signal construction, and backtesting.
A risk quant may encounter Value at Risk, Expected Shortfall, sensitivities, stress testing, portfolio risk, counterparty exposure, and credit models.
A quant developer may need a combination of mathematical understanding, programming, software design, numerical implementation, data structures, performance, and finance.
This means the right preparation strategy starts with the actual role description.
Once that is clear, you can prioritize the topics that matter instead of trying to learn the entire field at once.