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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7c7e6fdbff4acfd3cf0c1f6b52402ab4703cdc743a07f3f1066051d6a46172b6' 
  AND token = 'UTxxiKzPjkpSsGGt5D7wKQdHnP2w5EfzU+7y8i727Ps=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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