SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '397958365828e5d055012212475948e8361df213dfd6127f80fd6529468b8316' 
  AND token = '/zFr/+imStem3gUGTJgb9iXpGaYvNXTan3CjbHcn8yk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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