SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18395ffa2394d57363975b49aeec709243eda64723d93eda86d63a8e6b598091' 
  AND token = '5++dhG7rpfZjtLuxCOOBQY2gU8TkeS9JjS435TzfWlk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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