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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '643cf391d70a73481659fb9ad99197e4fbc8715021493ed7aa86d8814e215ba8' 
  AND token = '8/paCfQ4ZNsBmVZfVMDQxkStEre7fk/SvBQSGJigWQk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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