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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '51f673e55c04de8049b204d91f53513ac39904ffa4ca656e30621382551ac67b' 
  AND token = 'xvnu0FocuHx3SBzlbz79r+0i5UWDHc1vFejDAXikI7U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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