SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53862bf06de5be8af697df36df135c73e264e70f590ee01955946f09471649ed' 
  AND token = '2lefRGS+FgHse81mMBpnDxwgJVCdZQ8G2PKLZIIcZkc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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