SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db8500af503e775bec952fabcdc0ca328585c59e9db01762de4ba4e520932ece' 
  AND token = 'fYMLfiEDvmjkCnZpEIdsWuj9JdBR47BqXKkMKulUF+U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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