Bring a pot of salted water to a gentle boil. Add shrimp and cook for 2-3 minutes until pink and opaque. Transfer shrimp to an ice bath to stop cooking.

In a large bowl, combine lime juice, lemon juice, red onion, tomatoes, cilantro, and jalapeño. Mix well.

Fold the chopped shrimp into the marinade. Season with salt and pepper, and drizzle with olive oil if using. Stir lightly.

Cover and refrigerate ceviche for at least 20 minutes to enhance flavors.

Stir gently before serving in small glasses or cucumber slices. Garnish with cilantro and avocado. Serve with tortilla chips.