SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '916c206ec2942df27ed1e786843c8cbf1bb993d556bef928a9388381270f9c27' 
  AND token = 'RX1qOkRkJqG3BX/NljYhUD4zaHueAVrXlrbdymomhsM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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