SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b17c30a488a6121611e49f90c965eb2941152baac8ac2e129b8c10da754a79d' 
  AND token = '7mElHVl73NkajrplW2ObfqEnun1GdXjWnQqwNeW1t2U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}