SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc66e4bf7f239aadc20dc765b3c1b0d4ddc44fd55d5976f3ecaaa7c86a1e5210' 
  AND token = 'IwiVTtFGomhbWka0bpuPQfvpB3Ymer/ygM706dfpzOs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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