SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '831d03fd6a269497d0dc122ce4e378f07011df4d41e4cf7802edeb00bc46dd44' 
  AND token = '1vWbYr3U4TpPP1tPAmgoemayfiR11T52RpqqY+oUJCE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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