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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f21e8d9af7afcae1bcef2cdb1d7ca1d4cb3f124b3e0debc2383e3b678fa7a983' 
  AND token = 'JrUI7HeG1lkVmKHXQA2o7bHuqeafqymDEh+Xqh7kIxc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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