SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6306c007e9c9f050e79607378bad0c1e76b4338b01672e5030d592008aa65b95' 
  AND token = 'SSDKjVxnZuhGCyDZWzJKcIGrvw7icDCdu3KzZqlKstk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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