SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0839a5bac1129801fb82eac9a2de3d99a0ffc3863a10864ec76288092b9de332' 
  AND token = 'uOldZSWeLb9i00lHzgplaU6QpHGbEWSLngWC4JlMZvA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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