SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '433e9c15d3a67345f540201c59915b81606f6ed38f27f24541eb02fe2021538f' 
  AND token = 'CSImO8JMiFBW6l4ThMq8EQjTV9hQZCghBBp+RCXICjw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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