SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc302a69d62724dec141c3b576b8f8c4a978092e5565333603b7933635c8f7d8' 
  AND token = 'MumuH3JnshilzBPwYdNaMg7gjfWGCa7mcI+bTjwr4bc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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