SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2ed508d4a1498baeaac30e044f284269fbae8d2457d684a28314048f78d9318' 
  AND token = 'lgpChBmjjqMKD787UmMdrkPac59rmlvtc+oPNny6Gf4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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