SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29b886138bef3cc3680b0bd3d424da5ab85a28191f098135f894443286c07ae3' 
  AND token = 'zCR5O2n9zV0iY/z+fTvWF+KGG/dHEGUwBEb26wLdGGg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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