SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31b0e5f1cb3d0b2620d246567f528e405957ceb427bbd5d81aeb26e146803408' 
  AND token = 'XKC3CJFAdbbrR3vH+4gRkRXpwnTuetlbgp/ujU10wPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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