SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5439fc3268392a303031483957797b85fb3529d77c820f970111dd7aaad72d0d' 
  AND token = 'IQWQVrTaHs8XIJkTxFXJi3kLwlHYV+Woc2n8zYPtTnI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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