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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83b1c49697303c0972aa0e890c5a95a4add2c82785fbac406e87747a0457c700' 
  AND token = 'uTGWtok59vJx4UWNK66ikxVfonTeQT54a7AmZqoNFMA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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