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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd18c28aaf0ac34dca3417fe9f1aae05018f3aac47e97cc4e990dd42d038fe076' 
  AND token = 'hZNJoYHyb2nY8fcJQqi9xkg0D2dqD5ql/0Dw3qBiFFE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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