SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '855e95749e947d07889d7f72d88b536b59cf3db84013783686531a833c720d5d' 
  AND token = 'H71YlSPu+HkeBUqVubmYwlQNmZSUyfxg8+BNWjIqmi0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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