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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '55c1b59fa9beece64a0b7d6b2552db63d7c3e8a1c9b83318834022b82c3b721c' 
  AND token = '6SJl0IIxHwiyFJrgpbPYfKLpRDViuMD66nSzU65QBdY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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