SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '820e54657a85fbc6c92e5c548925e246c4f5def1e001dc941ed8bc7ef032063a' 
  AND token = '29bBkVyBtFI7OPtEmTZWXxfkPDluxfKOOW3fxLBuF28=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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