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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '87ddd168e0d68a81977dff3f7e10552f353a11b8fed148557ae8e24fabca7784' 
  AND token = 'JpLLFtqpNav84bAKtL+OVSur+uqYUjXaish1ejziTK4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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