SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f676e23aad721be264efacc8f0e204c7916e89a0ce1ffce4d7fd2eed68a3f4c8' 
  AND token = '4tKt4WrXwiypz1gUNOif3kA+MAPjFdCxQ8QIUGLI3wI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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