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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b50a7de267738d0d7340ee9039e95c1b1c50ddadcaed6b1587f917e85bd9f27f' 
  AND token = 'nVkjoSmzxomnMRIB+t8hJQ0Pc7mjqv1XrHevFgu+Pr0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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