SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68ae1ddd40a0048552f37dd2316b511f9f3d7ca892ff594c923db6323a415001' 
  AND token = 'agx0u56lrp/VPswgHOj3FToF8VtjUyE7sLfDDByR/oY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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