SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0fb9c84716ef2e571026327a828128da6de8795a0e752f96937c9be610bd974' 
  AND token = '6/IME9Sd7PCplYF5p+o+9irPgEkJxKYoOhm8u1uF5P4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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