SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a15bcff2303e537905b3e58bb70985978ecef9c691f706bd3779e29cbe005355' 
  AND token = '0ahTgBADxXUeqI+DaU9oKIpEGEWaBS96+LDqvrWvwsQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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