SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55ab5e32a70c6c821890966c5dce175eef54974ce2d2130b6c11f6f3e4265590' 
  AND token = '6cZ7Z3jeLEqo3MArT5e4zT0sSjFX9SrL4FYgra9CHB0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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