SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8399c5765b2764ec4acd39882866f194657a2915a480657cbf00e26d6a56e7cb' 
  AND token = 'joBFch5pwUB2qGZqvK9okYt+KOUNPuReRawZl0kKOUI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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