SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c59d6269685157580160c5ae9465b5bd1488f87a6afb390ce13ef9f114f9cf' 
  AND token = '6DarGMBrUOguyLo01aVnEiSi59IoVYa3ZeHpu+zwB9w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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