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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ac8624a4b664ba757b8990b9f10dee93f65c4dccb3549e387c512fb8d6fc87f4' 
  AND token = 'Q1+RDGpOGZuN6zuWmFXW4mQ6a6Sr92zwsLcVcwXz6is=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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