SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6dee05c1967365a0dd2d48d3726cfcc8af73f129defb3bb75b3f7a8777da8904' 
  AND token = '9Rtn/XLIdrbyoRBzzJEljIZ6UCr0hJijqVf4gkMJODY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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