SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5306ecf3e6f9455b1fefcfe3e7b980a609a84fd5a646479ac762a0544390455c' 
  AND token = 'j5kWjgPwGOeCKTuDRjgAP7QwkIPnJLopLx1XCCnHqjM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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