SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '48d7b1bbfbce79afb42507e097bc5da00b939c8c04b4c39119ac9ab1fa8646da' 
  AND token = 'NfFBQXMnR2r/fb3SjjC5GoJHbIcazwKocz3LnvztTMg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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