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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4ab79024b4f64e07d4c7046af957d7736c084498a3f3b738cd1d56859dc4a742' 
  AND token = 'XAINDg8URFdIBh1MLN7okurM1rwKWqdBoCW7zoeYy2Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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