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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '76db078ad028cff48b95f31e12dfde1c91fce7c26202e9f559ff3e0a13f71626' 
  AND token = '+n4EuOI3YkCnAKuXWbMy10OHNxXdmsz2VYvhGC9qICA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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