SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f476f275212567614fe4470a89514f621dc7f18b384112afe06206b40db79ead' 
  AND token = 'xqvZgtn8nZGGtm+UxqUmzHhxPsuJUtqIEib0xLOMp3A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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