SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd4fc53110db7436b798f1722abc7de88050d2a2a1359a7ab57e0028d45254678' 
  AND token = 'mXm0nTCsJ7w/K+95A7kIM9hWYoZ9t2RkrhAR+Nn0Uxk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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