SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6043872ecf38b8905161da0d27381fbc821763297a45c95305fee0a74d65025' 
  AND token = 'pt1JL8xlVRUQWcp+mGXvpwKZ0JDXODuHsCj73pHTxP4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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