SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5df1f0e6410dc7a35ea3a2285682dc571ee7137ee446b57599854dea369e0395' 
  AND token = 'e5MR9CbyWMXr0EKG194SfiiukeA60kl1wwiFhTIbqpk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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