SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c97cf9482fad385fb7e01019a1163dcf070fcd6de3e5241e9bf38b7f2f97615' 
  AND token = 'DMqalTAX5FQETha2+rYStJOugaJdsIZ2M8NZQBqjWbQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}