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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e551a183c53eb1aa8b651c9acfd0e8cdb02aee18d76f9eb8c9e817b2d1ab8f35' 
  AND token = 'nNkJ0ugncNuJQ3sGRet1AWHiiw4E0XMEGWS76n6zmdA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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