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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df55d6822737e1fd915d6554a9635600d37df3923a98e59878ca8593159ad115' 
  AND token = 'bmjKf68vFR3cZMuc+QS3+BwoxiU2B478+WSj7wPL0yU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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