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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '42a7be802a22c5d51435a2eee069f5603f2b91d2f31b4d19fb91de989be0ef21' 
  AND token = 'ScBmQa/iAMjk6Rou9hPoE448VKvmxHtip1wz0AIgj4Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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