Cook the spaghetti in a large pot of generously salted boiling water until al dente. Drain and rinse under cold water to stop the cooking. Let cool completely.

Halve the cherry tomatoes. Dice the cucumber into bite-sized pieces. Chop the bell pepper into small squares.

Finely dice the red onion. Cut the mozzarella into small cubes.

In a large mixing bowl, combine the cooled spaghetti with the prepared tomatoes, cucumber, bell pepper, red onion, mozzarella, and olives.

In a separate small bowl, whisk together the olive oil, vinegar, minced garlic, salt, and pepper until emulsified.

Pour the dressing over the spaghetti mixture and toss gently until everything is evenly coated.

Fold in the chopped fresh basil.

Cover the bowl and refrigerate for at least 30 minutes to let the flavors meld.

Taste and adjust seasoning with additional salt, pepper, or a splash of vinegar before serving. Serve chilled or at cool room temperature.