SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4016c92d686a41d95e80b97d89de6237a095674db7b6b6f3ec5d0d4deb8388d' 
  AND token = 'w0Sbpr5qBXwWmXqgtKAbFuLsTAGOfoPLTxRPYnG61/w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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