SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c75c275f60f969f409ac5f400ea368abc19bffa7bd11adce42def9ef2f467ea3' 
  AND token = 'zQa61vcObAwCXMrsaM4vcGqopVzrXsNhNEhhgflVLGo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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