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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b81b12a15595716d51fd7850b7ccdaab45a2044bc22d15659f7deba1527db00' 
  AND token = '/4xv1RsX8MgHOavE7ULozDK9//UtmlffrKUr9C7JLjs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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