SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18923effc57cfc232758ff606aee8835cd21744ca4ad7bfe4aa473693b85f77a' 
  AND token = 'dRWkmH3HmzO371FLlFq54UZP/io41vY+ZlCBHj+N5qk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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