SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f3888615fd2a4a54862035c9c402d5a64e7e677788b6e08a9353777337e05a' 
  AND token = 'figuSTNhfJAoSUyd/YaFQb9kA99UDQC2CHbAphI0XAk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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