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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4e8f23878583a8ae30fc2b168ad5f9d0870b7188b5e4c9a063bb01a136bc8637' 
  AND token = 'NL3NExPzD20rPLhlJHLjQktlGJ8Dd8LzobXKxg/EwWk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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