SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5be6a80a7f06d1a2446f61302c7dc2bdeff1068f016a6bef15490460f499e43' 
  AND token = 'GrsFgmiFqhNDPvqNCgEuFOvGA+hmm/hNBJJzVz8SasA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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