Drain and rinse the soaked chickpeas thoroughly, ensuring they are patted dry.
Place chickpeas, onion, parsley, cilantro, garlic, cumin, coriander, salt, pepper, and cayenne into a food processor.
Pulse the mixture until it reaches a coarse, crumbly texture; avoid over-processing into a paste.
Transfer the mixture to a bowl, stir in the baking soda, cover, and refrigerate for 30 minutes.
Form the chilled mixture into balls or small patties using approximately 2 tablespoons of mixture per unit.
Fill a deep skillet or pot with 2 inches of oil and heat to 350°F (175°C).
Fry the falafel in batches for 3 to 5 minutes until the exterior is a deep golden brown and crispy.
Remove falafel and drain on a wire rack or paper towels.
Construct the bowls by partitioning 1/2 cup of rice into four serving dishes.
Add 4 to 5 falafels to each bowl, followed by scoops of hummus and tzatziki.
Top with diced cucumbers, tomatoes, pickled onions, and feta cheese.
Finish with a drizzle of tahini sauce and serve immediately.