SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e786476a8bec307bd96d74645f73643253fd8dcf1a636e8bf92c4aae958e70' 
  AND token = '9EbIdyJ7UqV0CyDZA3z/Hj9D5oMAJ3oK6jdT1QXHiXo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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