SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18cf92f4be883daf611d2614edb6f9d1b7166c915d78a6d36108f7271d756b23' 
  AND token = 'MLCDJATbb838YWBft8V0GTASWo95bjqj+bwSKCdg9HQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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