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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a57a8ee89006242159d0114c8f5de4c09b6c0e7b901a28a56b64595964a45210' 
  AND token = '5YQYx3wlQetXYkkKusFpNUt7ui4LEU7qtryedNeEEaE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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