SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc929dfbbc016bb8bb80649e96a6635fa7cd3fef2b134dede4bea1c9503a8dc0' 
  AND token = 'xQMR+LsmWanFDnBo5PtmixUmMqlBGujwAwIroG2gHyM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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