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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b553b0deef82fcb93e67097d8df58477529506c3c7c77ae1f741c14578e562ab' 
  AND token = '9HnM/axvQC5syEg93BEwy2wMllToudmf/slmOqgDTWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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