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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e78b31ac056672573165bb8212e403078888121249a202e49093a6c4f0be58de' 
  AND token = 'uViX00/L0RRv7Q87skzusi+olb20IaoWgAPI+NrpGFc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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