SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b552b8bbb7d32a1602bba3a208da32e545ca9cd16737988dc04ab046291ea42' 
  AND token = 'QmIr0CAwp7qBXKwZGwvsIfYZ5RUFTTm6WOpml+MtmCA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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