SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '320b04b85efb31fe2f07273360c49841aa541d9d467d77c24f96d0aff1491daa' 
  AND token = 'YEy7rO/EZEYAbEyTiiG5AV0bsKgi/wyuSS9rhDXGldI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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