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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9cec24ea8869a382fed6dc8bc9c9184e16b6066d6cca35b4da14e1ad5d43e21' 
  AND token = '5AzVfG5xLJ8kH6PoLjY1clMrntzMUuVICO1kEQ2osvA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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