SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '677a28dda5cec60a20a968865f97a500b5299b403a85cba3da0907dc09f460e7' 
  AND token = '3qLYuOaMMKQ/8t7GrtWtHCViOiSlgrno4Afls5oZPsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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