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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9667b6aa75f4a57073cc0eaa23e90794e42e008f66764d22184e354fd02c1c7' 
  AND token = 'UQ9XSR5rGTwfj084MZCDElXlpEPC2CaQz+BR7mXbw2E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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