SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50db500b84bc0451dfaf569dc32b61adec5daae62bb11b07bfbc94f76f5be86c' 
  AND token = 'UMcZXbxF6IS7UuLMfBeRZcPovZJ8Y1tCzxvUQvDZOWQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}