SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76ef24aac0becb892595d09f8bea2da2c1dd3a3d59d002935c82ad2ca8d00c95' 
  AND token = 'KvtiuAj17TFZBCNol1hNCz4KZ+wll+sPLyRTEr1e6Ko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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