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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b7a6dc50ae764353108518d574fb6bb06d33c5fc889d31462a4e7b01b0a962c1' 
  AND token = 'oAvR/gW3Y7lDf9CHSgi1Vkf5O8QAtHJCe1KSTFiagw4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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