SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ef87813d782857f5fc65f9df013f4105a4b2dffe838e878894657b5668544eb' 
  AND token = 'TeEve+ekih65m2VGOguOqxzXLetfb4jUEoYdul5888w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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