SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f4be06a2d757850aeae594111580e16ac654d824f0f1690b9bc4d061af532af' 
  AND token = 'szxn/IpKlmqdwWeZ+pg6A2wyQ+B8Xa4JYt2pm/ABv3A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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