SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91cae3177ec70b512d4acf609256853738eec9e582a90e44687f248ec4448c82' 
  AND token = 's/vRYf8x6HlRGUenG+snJMeZ0twtTOmiBzKCrpOlLSg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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