SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '531b860ca5f977d81cbb1d5e33cf2d61de5037d67119e55cc940a0ea6eb1a9f4' 
  AND token = '/CLM5Us0QwqZeWmpQsA1syk36bnylfAYdjtVHHDrAts=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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