SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '678189ae38da0086d3775b34081f67c58e68446cd4a6fc0b384a2f490ecea77c' 
  AND token = 'Db5+Js/3RxShdJgQPDg+A2KpQiwaWvgY/1x8BTtgBzs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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