SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4bbec12981b384af0221d3ce45fd971143c5b84b031d82ecbaeaa0abf380f75' 
  AND token = '6TWRxbfdO13jrpD2lfW7hU4RuRPpXBqlNYeWdY0U2yc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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