SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '96e9f1e16a65d10f0b235284d6855bad99ae3d5cb3e583901209d9edbcd992de' 
  AND token = '6l8texIGOCPpBe1MGg9tUH03RuiPqnMuRKcxhwerQUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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