SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '138ff54ca129df00aea77f6a0db68654dc4956168e151dd29a428e10be67411d' 
  AND token = 'cBuroz3Z0OJXcvWsQl24FbdP2fdr1kxWTrOjQkmQYcY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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