SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '421859ed3b9152cdf21f25ce509c7c6b245d85b7e8ef723b6c1d4637fca63f1d' 
  AND token = '/tZBPrrYJ7tzICfiAafsty2gIJ/JB1G+gA+q1mdw9jg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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