SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd43d384197baf758cc0f3db20a31815a6668d3d21198120785a45606268be8ed' 
  AND token = 'KVncO/jFc2/pUq7sctacMABkZYGIISbW0H2AowG7nVE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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