SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7e336fef522a80f55af58ab19430d55f21a5e37d765094cfedc5dac1af1801a' 
  AND token = 'FUYi+MIa5jeQmvGm0HvxBt1tMDzTTRPgmAarNBhsXEM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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