Koby started out in the youth ranks at Woodford United in Northamptonshire before being spotted by a Birmingham City scout in 2012. He moved into the football and education development programme run by their community department, but was soon recruited into the main development system. He signed his first professional deal with Blues in the spring of 2013 and made his first team debut as a 78th minute substitute in a 3 - 2 home loss to Wolves in April 2013. He then made his first competitive start against Plymouth Argyle in the League Cup 1st Round in August 2013 with Blues winning 3 - 2 after extra-time.

In March 2014 he joined Lincoln City on a youth loan for the remainder of that season and he then began the 2014-15 campaign out on loan again at Cheltenham Town before being recalled by Birmingham City in mid-September. He enjoyed a brief run in the Blues first team after Gary Rowett took charge and he signed a new two-year contract at the end of the 2014-15 season, however his time at St Andrews began to stall. He returned to Cheltenham Town on loan for the first half of the 2016-17 campaign, but his progress was hampered by injury and he was freed by Blues at the end of his contract in 2017.

He then spent two seasons with Macclesfield Town with the Cheshire outfit winning the National League title in 2017-18 to secure promotion to the Football League. He was released in the summer of 2019 and then unfortunately suffered an achilles injury while on trial at Walsall that kept him out of the game for a few months before he returned to training with Kidderminster Harriers early in 2020. He was offered terms by Harriers for the 2020-21 season that eventually ended prematurely with the covid-19 outbreak. He was released in the summer of 2021 and he subsequently signed for Dover Athletic in August 2021. Hindered by a 12-point deduction from the National League, the Kent outfit were relegated at the end of the 2021-22 season and Koby was not retained. He spent the 2022-23 campaign with National League outfit Maidenhead United before signing for Hereford FC in July 2023 after a successful trial spell. He has made 20 appearances for the Bulls this season with 13 of those coming off the bench. grabbed his first goal for the club against Redbridge in the FA Trophy.