SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4cf50368024b32cab7b3a558aa2f6337296008ad62d71d68639baf675984687' 
  AND token = 'FuGKsNgXKMmYJU4lcV61ck4mEyipdcHHFPmjvj1sB2s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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