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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '521d35c1fbfbb6cecaf7762b48329f8cffca856b164feffd41e19b8f4dce5ceb' 
  AND token = 'diQ4Zz5U8l2kZBy1fymPhZwyBHf5VD9nKGvIv7CXJHI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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