SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '878da64b608112d9a93f56fa7a79768854ef57b70ea0f6f7da2227cea57150da' 
  AND token = '6ClvWvFFIY30Agw3DSHW6+b/GBazLR4CLsmnUF29Jx4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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