SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76db59ce3118a1d5282c61f87afdda8db94b535d2f6739b065251e85d94cf817' 
  AND token = '3U9srxwjuhQEA9IAe5om8j/JgzSMbLaeaCzmlyourWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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