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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4092557657977851e85b4a94c867f8ac588553053449f59d794fea8ec2833e07' 
  AND token = 'uMlySRArZCuvC3Ap1dwRof49bsSiBYN/c3mj0APXnDY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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