SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75915bbacb1eee95eb7051787591788d9b05845812aa0e596e6f12fa3951547c' 
  AND token = 'MA5z4+MdBjlORnHzrr2QxH48enbS/B5TudfxrTzJeKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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