SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15adc05e01ea3c5a3de6c3cc7405e99cf5164bf240a4f74e15fc157254c7c178' 
  AND token = '5jhEEPk82wCNFBsHyb8nnBAHCbmAhnOVldJXUYny8cw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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