SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '338fd356270335393efea6b8148acfb415eece5dcf91034cce7948af0323be49' 
  AND token = '36Vef/AHsctt9yWb4KHd9EyfoYRa8pYyijfy8muP8SE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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