SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e087ea1d56738590985818b4e0e48da748ecf55e715669615ef1af4addb61572' 
  AND token = '8rQSoUrVoWUtav/yORiSgDYZkjSdfxGenc9wMsfRF84=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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