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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ff12508215a67d691b2711d229b8312d9cee6032b2c45b39bbbcdce3c5b58b8' 
  AND token = '5EhFP7HUraniBZme7yHdLWxs7QeWfFOS1bM/gj0JMbc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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