SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dcfa12709ba9fc2bd4925786dd9d18f5ba65d811d2342b8fea9b13e9f4323e8c' 
  AND token = 'kgmdDQlTnvYUGr96V9c0pEBgEn8tergWsRxuLYGOhTk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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