SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8dc82bd99f832471a8b1fac57ce6a6ba45d2bbf378e2d23591fb2af91543d697' 
  AND token = '+MSeIE72chHj7PXO02/PqZGA3a3QjOKS1t2UlJvhklg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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