SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4202ec1b18b7ef981cc8420ff83f19a1275961771eca97d44f27136d952e9c8' 
  AND token = 'XtMRqDDicSQjt7oIfxYVCDb7mOSh54XHVSpA+nV/1ik=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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