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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8476c61ba332ea14910d6157046e3e317e1670a15a6d6d79069eee614ed4954' 
  AND token = 'QYxi5xcNTZtfXRsECKFqntLn66gBeR0kP9v1nbd/gw4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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