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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f5494bb91d6fcb31661bab84e400c69a4e3ee93f4ac301361aa2dac54036d0d3' 
  AND token = '2jIviYoaKJfsnf/e4YEWCKtdSRBcuZmDh2zzjiTGsc8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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