SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f51da9b32994b7056ea5b044a32aadb2213d517abe9c083dede7ad21b336d978' 
  AND token = '4PxZBYHTFfgdtDlU/GPzQmQf/99lpCXHXwlTdMHjtqI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}