SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b892c1f105acee0128fcf92e8a8da67c7cc83216985a8499410878b64916e67' 
  AND token = 'S+S1/W+ollHSEzlVSkI0u7B1mXyhvAZRCY4gBYlTsn4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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