SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3859439cf2c949850b18fbb9f6a4c4d377ab4be8317cb1231b52150fee716788' 
  AND token = 'fSSACPZGoP0/FSN3/qrRTungbu1wejI16DMI6FQsYOc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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