SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79de872455418124bc5c46beccf254de46fe70944613d57fa98a5e8451123e7a' 
  AND token = 'JuoPreDbTj57Re7wqgavYcLemqz/PbFt0gMcUKpdrSo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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