SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a737dd3646d68c5ec0379ad8712959cde5e21668970de29f70c39b34e5955f6' 
  AND token = 'R8Tw2AvI+fu8Kx1fLFdmJ+3RIqIlkbrjKrB+BEouPMQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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