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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9a6f3c5b99a5c81138288029ee4a6097cd6041db8a98c65319d1b5284d452c12' 
  AND token = 'AMnt2Yeu6m8kfLIFn5lRuQ8b2qG2Q/gLA/KjMK8f2Hs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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