SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '48ab670590119891014140958316720d3324553d9fbb38f76c5ddccc17bfff77' 
  AND token = 'n+iqhUCUN/EngZnVSvMlWBKYwLmAFbdE+T+owixdeAA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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