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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18fc3a4f9544a5ebf2f2fcc4cf75d28653e055b5d5372c07dabd8f3dd9b84a36' 
  AND token = 'JCTPcsHZKFSWtnFNUfJ6udY2wdsPDe3JdQtd+xXo7FM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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