SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cfa871b67379bda381c28e4de27c98846b9947d90691988286497f1b861ed6a2' 
  AND token = 'Dqncno3U7YaL+3RBquFyxo4Ouvqo8ujqvWZmArE1pqQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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