SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9a38420d7e1c6f60790659943d8bd4eef94f634888f086ad04cbd9a0828de92' 
  AND token = 'S917xuqyum94nHiASeh4M4RJjmSzyvFMSBXm+cOxhZ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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