SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f188c76f14fea01264691974338066ebf7910c713cabc11fb1a9e3641fd120bc' 
  AND token = 'gjnJA9mTvSgZtYq7teaDM+TRaky4jSwfnsS7l/pmAdE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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