SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c273ab2a4344ed25894b5fe205322e00477b3432eae0ae5d074b55fd2ae09389' 
  AND token = 'cMTIasnLebpHjKt/UxWVzyRPvLzxgtrSBc+hyTxKPZQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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