SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '87ca4754a396185d54e52ddb209209b3671ad14ab32a86007a552cd20862e4af' 
  AND token = 'MmgErKFBqLRVF21XaBsfCng32VHVAO3mlm2JH7ZzSWk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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