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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39e70aec7859a991f19177a4d6f193d61dff4a05dcefcd249f5782b345bf5f05' 
  AND token = 'iPMmsAjPq7yrtMWiFT2D7EsFfO0JfB5T+SQK5HQjupI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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