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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c58f3995df2b3d848f1e5a49ef945295318b215480984314db94dbdf9859bf14' 
  AND token = 'f1LnhPGNQdpfsiiiJ/apgeVUUzPbz125qEZEtfhRsn4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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