SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51bdad245eedd4c9851a4afd8786440ce6419fe2aff90c4c59cea5ddd3252bbb' 
  AND token = 'YTg2Vussup6hOUGvyCRt/7BcEShgYdEPMGo6y/KSJjU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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