SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b1fe875df35528eaaceb5d36c1975bc0662537685b033def2e7d92d293af3fd' 
  AND token = 'KUvokvHyxqZEYgPq5bJqy+LF9ZqXK75gI/ykpPIwQso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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