SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5621e891432afb0fa77b022787449ae8a8f3db29f00012fb4d0f026a921f67bb' 
  AND token = '0OD3dRcakJNBRzNgAWUy64OUpZrUyGp/7jQ0NIQLzUc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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