SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '270b577266423d0a0775e03d61ea78ba91d1a2bf88a992e9858e1aeb1fc4a657' 
  AND token = 'oTv1BPwb8dhrXZ3GO7IqYvNKZTNexQLpjQYTwndV8IY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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