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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e7a0942ac77191b6ebf2a132f9df98d8c37c0eee2d6fb29ab214d7ae7b4a3c4' 
  AND token = 'c4Kjw8QkUqhUY78DpUTaCXaDnlxklots/php+QbO0Nk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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