SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b1dd4dcfd1008e24732ad02a1205c32428752cb97dbf841c403589758b2a32' 
  AND token = 'v99zShpP+l923NCpR5WR9MkJY2R1fb98J/YqDMzAbig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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