SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79e89f979ec2b274c11d1a284e21d8f0d2b42d6f4a23ee1691f2242b8bd332cd' 
  AND token = 'vTwThJCm+YxVxsQxK6QXmKpm9AnClx5LPtqsekt9qu0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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