SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8781c031160a777aa12b52283a1514ca689a353b2eafee92f8676d8cadd6377' 
  AND token = 'k9dYrdnAtJVdfEwaAymON7U6ihWjYtSlzWLr8biHqac=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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