SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6b26b72e95d542e8a9a35ce8246780b84a9779106665387bc8ede75ed370f28' 
  AND token = 'EpU07ETueDCYWdic/CRpk4VcurKDimOZ2SOWVcHwODw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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