SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90d1fdf0ba1c684796ea67af711ec1796df447b55a3ec263f1ca3d63651debe3' 
  AND token = '3/KP4IPzUZ29nnRQrSnXlLjGRqlz1vnj+BFpuGhA7f0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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