SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd39a219db34ecff9a9f466240ef3a0e5bfe14e31d49b894314a688cfb9517d55' 
  AND token = 'X8VEa0chn0Jzwf1WsE+Hh1Y0ogFErTGnmnLC/8vBuvU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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