SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51958b82ad2c1e573e52b31fa522fe6c60f057232e8491290c515ba971c869b5' 
  AND token = 'j+MwjisOBy3sKhDwyg8JtQ518QK8YvdlVTgcYexfxeI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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