SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e64adcd80d17b71a5ca8ad1fa1e2def60eacb46407f33136ecfc3ff52a37569' 
  AND token = '6k4cMvTKE4GHzcpMS7ek2lzjhHwDhHNrQjG/pCT1EyY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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