SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '709df1b58d7c77231a757757e2c5056897814e53725800917df7022d0f3157a7' 
  AND token = '+fBlbe3HPuzSmPZEv1JZG/AKf2NPEx+VQBGhpFOQ5Ng=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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