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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '851d4db78282b4395589791826eabadee487422c338d4a176191bc4a8c535f71' 
  AND token = '/D+LoEiFkdQH0OyWv7BNl0yOuwCSURe1HI7ns3pg4Gs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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