SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b15d7cb7ded31b8eea43ad9a354af487921e453853e419cfec38cbde088c3fea' 
  AND token = 'm5GHQxTrVTBUIySmUWxjmVhvaNp30zpBLk0pBWz3lvI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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