SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7dadb650d3d7ffd9f3065af38bb955b2ea0752a41df365cccf00c873a0f82a3' 
  AND token = 'rVsmskNYtG/XmSdmJ2/wq3wtLAHyRvBep8LWgMDLi9g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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